Tài liệu PHP

PHP Tutorial

PHP is a powerful tool for making dynamic and interactive Web pages.

PHP is the widely-used, free, and efficient alternative to competitors such as Microsoft’s ASP.

In our PHP tutorial you will learn about PHP, and how to execute scripts on your server.

 

PHP Quiz Test

Test your PHP skills at W3Schools!

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PHP References

At W3Schools you will find complete references of all PHP functions:

  • Array functions
  • Calendar functions
  • Date functions
  • Directory functions
  • Error functions
  • Filesystem functions
  • Filter functions
  • FTP functions
  • HTTP functions
  • LibXML functions
  • Mail functions
  • Math functions
  • Misc functions
  • MySQL functions
  • SimpleXML functions
  • String functions
  • XML Parser functions
  • Zip functions

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The PHP Certificate documents your knowledge of PHP and SQL (MySQL).


PHP Introduction



PHP is a server-side scripting language.


What You Should Already Know

Before you continue you should have a basic understanding of the following:

  • HTML/XHTML
  • JavaScript

If you want to study these subjects first, find the tutorials on our Home page.


What is PHP?

  • PHP stands for PHP: Hypertext Preprocessor
  • PHP is a server-side scripting language, like ASP
  • PHP scripts are executed on the server
  • PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
  • PHP is an open source software
  • PHP is free to download and use

What is a PHP File?

  • PHP files can contain text, HTML tags and scripts
  • PHP files are returned to the browser as plain HTML 
  • PHP files have a file extension of “.php”, “.php3″, or “.phtml”

What is MySQL?

  • MySQL is a database server
  • MySQL is ideal for both small and large applications
  • MySQL supports standard SQL
  • MySQL compiles on a number of platforms
  • MySQL is free to download and use

PHP + MySQL

  • PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)

Why PHP?

  • PHP runs on different platforms (Windows, Linux, Unix, etc.)
  • PHP is compatible with almost all servers used today (Apache, IIS, etc.)
  • PHP is FREE to download from the official PHP resource: http://www.php.net
  • PHP is easy to learn and runs efficiently on the server side

Where to Start?

To get access to a web server with PHP support, you can:

  • Install Apache (or IIS) on your own server, install PHP, and MySQL
  • Or find a web hosting plan with PHP and MySQL support

PHP Installation



What do you Need?

If your server supports PHP you don’t need to do anything.

Just create some .php files in your web directory, and the server will parse them for you. Because it is free, most web hosts offer PHP support.

However, if your server does not support PHP, you must install PHP.

Here is a link to a good tutorial from PHP.net on how to install PHP5: http://www.php.net/manual/en/install.php

Download PHP

Download PHP for free here: http://www.php.net/downloads.php

Download MySQL Database

Download MySQL for free here: http://www.mysql.com/downloads/index.html

Download Apache Server

Download Apache for free here: http://httpd.apache.org/download.cgi


PHP Syntax



PHP code is executed on the server, and the plain HTML result is sent to the browser.


Basic PHP Syntax

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.

On servers with shorthand support enabled you can start a scripting block with <? and end with ?>.

For maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.

<?php
?>

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.

Below, we have an example of a simple PHP script which sends the text “Hello World” to the browser:

<html>
<body>

<?php
echo “Hello World”;
?>

</body>
</html>

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text “Hello World”.

Note: The file must have a .php extension. If the file has a .html extension, the PHP code will not be executed.


Comments in PHP

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

<html>
<body>

<?php
//This is a comment

/*
This is
a comment
block
*/
?>

</body>
</html>


PHP Variables



A variable is used to store information.


Variables in PHP

Variables are used for storing a values, like text strings, numbers or arrays.

When a variable is declared, it can be used over and over again in your script.

All variables in PHP start with a $ sign symbol.

The correct way of declaring a variable in PHP:

$var_name = value;

New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let’s try creating a variable containing a string, and a variable containing a number:

<?php
$txt=”Hello World!”;
$x=16;
?>

PHP is a Loosely Typed Language

In PHP, a variable does not need to be declared before adding a value to it.

In the example above, you see that you do not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on its value.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP, the variable is declared automatically when you use it.


Naming Rules for Variables

  • A variable name must start with a letter or an underscore “_”
  • A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
  • A variable name should not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($my_string), or with capitalization ($myString)

PHP String Variables



A string variable is used to store and manipulate text.


String Variables in PHP

String variables are used for values that contains characters.

In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text “Hello World” to a string variable called $txt:

<?php
$txt=”Hello World”;
echo $txt;
?>

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate the string.


The Concatenation Operator

There is only one string operator in PHP.

The concatenation operator (.)  is used to put two string values together.

To concatenate two string variables together, use the concatenation operator:

<?php
$txt1=”Hello World!”;
$txt2=”What a nice day!”;
echo $txt1 . ” ” . $txt2;
?>

The output of the code above will be:

Hello World! What a nice day!

If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.


The strlen() function

The strlen() function is used to return the length of a string.

Let’s find the length of a string:

<?php
echo strlen(“Hello world!”);
?>

The output of the code above will be:

12

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).


The strpos() function

The strpos() function is used to search for character within a string.

If a match is found, this function will return the position of the first match. If no match is found, it will return FALSE.

Let’s see if we can find the string “world” in our string:

<?php
echo strpos(“Hello world!”,”world”);
?>

The output of the code above will be:

6

The position of the string “world” in our string is position 6. The reason that it is 6 (and not 7), is that the first position in the string is 0, and not 1.


Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference.

The reference contains a brief description, and examples of use, for each function!


PHP Operators



Operators are used to operate on values.


PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator Description Example Result
+ Addition x=2
x+2
4
- Subtraction x=2
5-x
3
* Multiplication x=4
x*5
20
/ Division 15/5
5/2
3
2.5
% Modulus (division remainder) 5%2
10%8
10%2
1
2
0
++ Increment x=5
x++
x=6
Decrement x=5
x–
x=4

Assignment Operators

Operator Example Is The Same As
= x=y x=y
+= x+=y x=x+y
-= x-=y x=x-y
*= x*=y x=x*y
/= x/=y x=x/y
.= x.=y x=x.y
%= x%=y x=x%y

Comparison Operators

Operator Description Example
== is equal to 5==8 returns false
!= is not equal 5!=8 returns true
> is greater than 5>8 returns false
< is less than 5<8 returns true
>= is greater than or equal to 5>=8 returns false
<= is less than or equal to 5<=8 returns true

Logical Operators

Operator Description Example
&& and x=6
y=3(x < 10 && y > 1) returns true
|| or x=6
y=3(x==5 || y==5) returns false
! not x=6
y=3!(x==y) returns true

PHP If…Else Statements



Conditional statements are used to perform different actions based on different conditions.


Conditional Statements

Very often when you write code, you want to perform different actions for different decisions.

You can use conditional statements in your code to do this.

In PHP we have the following conditional statements:

  • if statement – use this statement to execute some code only if a specified condition is true
  • if…else statement – use this statement to execute some code if a condition is true and another code if the condition is false
  • if…elseif….else statement – use this statement to select one of several blocks of code to be executed
  • switch statement – use this statement to select one of many blocks of code to be executed

The if Statement

Use the if statement to execute some code only if a specified condition is true.

Syntax

if (condition) code to be executed if condition is true;

The following example will output “Have a nice weekend!” if the current day is Friday:

<html>
<body>

<?php
$d=date(“D”);
if ($d==”Fri”) echo “Have a nice weekend!”;
?>

</body>
</html>

Notice that there is no ..else.. in this syntax. You tell the browser to execute some code only if the specified condition is true.


The if…else Statement

Use the if….else statement to execute some code if a condition is true and another code if a condition is false.

Syntax

if (condition)
   code to be executed if condition is true;
else
   code to be executed if condition is false;

Example

The following example will output “Have a nice weekend!” if the current day is Friday, otherwise it will output “Have a nice day!”:

<html>
<body>

<?php
$d=date(“D”);
if ($d==”Fri”)
   echo “Have a nice weekend!”;
else
   echo “Have a nice day!”;
?>

</body>
</html>

If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces:

<html>
<body>

<?php
$d=date(“D”);
if ($d==”Fri”)
   {
   echo “Hello!<br />”;
   echo “Have a nice weekend!”;
   echo “See you on Monday!”;
   }
?>

</body>
</html>


The if…elseif….else Statement

Use the if….elseif…else statement to select one of several blocks of code to be executed.

Syntax

if (condition)
   code to be executed if condition is true;
elseif (condition)
   code to be executed if condition is true;
else
   code to be executed if condition is false;

Example

The following example will output “Have a nice weekend!” if the current day is Friday, and “Have a nice Sunday!” if the current day is Sunday. Otherwise it will output “Have a nice day!”:

<html>
<body>

<?php
$d=date(“D”);
if ($d==”Fri”)
   echo “Have a nice weekend!”;
elseif ($d==”Sun”)
   echo “Have a nice Sunday!”;
else
   echo “Have a nice day!”;
?>

</body>
</html>


PHP Switch Statement



Conditional statements are used to perform different actions based on different conditions.


The PHP Switch Statement

Use the switch statement to select one of many blocks of code to be executed.

Syntax

switch (n)
{
case label1:
   code to be executed if n=label1;
   break;
case label2:
   code to be executed if n=label2;
   break;
default:
   code to be executed if n is different from both label1 and label2;
}

This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.

Example

<html>
<body>

<?php
switch ($x)
{
case 1:
   echo “Number 1″;
   break;
case 2:
   echo “Number 2″;
   break;
case 3:
   echo “Number 3″;
   break;
default:
   echo “No number between 1 and 3″;
}
?>

</body>
</html>


PHP Arrays



An array stores multiple values in a single variable.


What is an Array?

You have already learnt that a variable is a storage area holding numbers and text. The problem is, a variable will hold only one value.

An array is a special variable, which can hold more than one value, at a time.

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

$cars1=”Saab”;
$cars2=”Volvo”;
$cars3=”BMW”;

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The best solution here is to use an array!

An array can hold all your variable values under a single name. And you can access the values by referring to the array name.

Each element in the array has its own index so that it can be easily accessed.

In PHP, there are three kind of arrays:

  • Numeric array – An array with a numeric index
  • Associative array – An array where each ID key is associated with a value
  • Multidimensional array – An array containing one or more arrays

Numeric Arrays

A numeric array stores each array element with a numeric index.

There are two methods to create a numeric array.

1. In the following example the index are automatically assigned (the index starts at 0):

$cars=array(“Saab”,”Volvo”,”BMW”,”Toyota”);

2. In the following example we assign the index manually:

$cars[0]=”Saab”;
$cars[1]=”Volvo”;
$cars[2]=”BMW”;
$cars[3]=”Toyota”;

Example

In the following example you access the variable values by referring to the array name and index:

<?php
$cars[0]=”Saab”;
$cars[1]=”Volvo”;
$cars[2]=”BMW”;
$cars[3]=”Toyota”;
echo $cars[0] . ” and ” . $cars[1] . ” are Swedish cars.”;
?>

The code above will output:

Saab and Volvo are Swedish cars.

Associative Arrays

An associative array, each ID key is associated with a value.

When storing data about specific named values, a numerical array is not always the best way to do it.

With associative arrays we can use the values as keys and assign values to them.

Example 1

In this example we use an array to assign ages to the different persons:

$ages = array(“Peter”=>32, “Quagmire”=>30, “Joe”=>34);

Example 2

This example is the same as example 1, but shows a different way of creating the array:

$ages['Peter'] = “32″;
$ages['Quagmire'] = “30″;
$ages['Joe'] = “34″;

The ID keys can be used in a script:

<?php
$ages['Peter'] = “32″;
$ages['Quagmire'] = “30″;
$ages['Joe'] = “34″;

echo “Peter is ” . $ages['Peter'] . ” years old.”;
?>

The code above will output:

Peter is 32 years old.

Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array
   (
   “Griffin”=>array
   (
   “Peter”,
   “Lois”,
   “Megan”
   ),
   “Quagmire”=>array
   (
   “Glenn”
   ),
   “Brown”=>array
   (
   “Cleveland”,
   “Loretta”,
   “Junior”
   )
   );

The array above would look like this if written to the output:

Array
(
[Griffin] => Array
   (
   [0] => Peter
   [1] => Lois
   [2] => Megan
   )
[Quagmire] => Array
   (
   [0] => Glenn
   )
[Brown] => Array
   (
   [0] => Cleveland
   [1] => Loretta
   [2] => Junior
   )
)

Example 2

Lets try displaying a single value from the array above:

echo “Is ” . $families['Griffin'][2] . ” a part of the Griffin family?”;

The code above will output:

Is Megan a part of the Griffin family?

PHP Looping – While Loops



Loops execute a block of code a specified number of times, or while a specified condition is true.


PHP Loops

Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In PHP, we have the following looping statements:

  • while - loops through a block of code while a specified condition is true
  • do…while – loops through a block of code once, and then repeats the loop as long as a specified condition is true
  • for - loops through a block of code a specified number of times
  • foreach - loops through a block of code for each element in an array

The while Loop

The while loop executes a block of code while a condition is true.

Syntax

while (condition)
  {
  code to be executed;
  }

Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>

<?php
$i=1;
while($i<=5)
   {
   echo “The number is ” . $i . “<br />”;
   $i++;
   }
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

The do…while Statement

The do…while statement will always execute the block of code once, it will then check the condition, and repeat the loop while the condition is true.

Syntax

do
  {
  code to be executed;
 
}
while (condition);

Example

The example below defines a loop that starts with i=1. It will then increment i with 1, and write some output. Then the condition is checked, and the loop will continue to run as long as i is less than, or equal to 5:

<html>
<body>

<?php
$i=1;
do
   {
   $i++;
   echo “The number is ” . $i . “<br />”;
   }
while ($i<=5);
?>

</body>
</html>

Output:

The number is 2
The number is 3
The number is 4
The number is 5
The number is 6

The for loop and the foreach loop will be explained in the next chapter.


PHP Looping – For Loops



Loops execute a block of code a specified number of times, or while a specified condition is true.


The for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

for (init; condition; increment)
  {
   code to be executed;
  }

Parameters:

  • init: Mostly used to set a counter (but can be any code to be executed once at the beginning of the loop)
  • condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
  • increment: Mostly used to increment a counter (but can be any code to be executed at the end of the loop)

Note: Each of the parameters above can be empty, or have multiple expressions (separated by commas).

Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>

<?php
for ($i=1; $i<=5; $i++)
  {
   echo “The number is ” . $i . “<br />”;
  }
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

The foreach Loop

The foreach loop is used to loop through arrays.

Syntax

foreach ($array as $value)
  {
   code to be executed;
  }

For every loop iteration, the value of the current array element is assigned to $value (and the array pointer is moved by one) – so on the next loop iteration, you’ll be looking at the next array value.

Example

The following example demonstrates a loop that will print the values of the given array:

<html>
<body>

<?php
$x=array(“one”,”two”,”three”);
foreach ($x as $value)
  {
   echo $value . “<br />”;
  }
?>

</body>
</html>

Output:

one
two
three

PHP Functions



The real power of PHP comes from its functions.

In PHP, there are more than 700 built-in functions.


PHP Built-in Functions

For a complete reference and examples of the built-in functions, please visit our PHP Reference.


PHP Functions

In this chapter we will show you how to create your own functions.

To keep the browser from executing a script when the page loads, you can put your script into a function.

A function will be executed by a call to the function.

You may call a function from anywhere within a page.


Create a PHP Function

A function will be executed by a call to the function.

Syntax

function functionName()
{
code to be executed;
}

PHP function guidelines:

  • Give the function a name that reflects what the function does
  • The function name can start with a letter or underscore (not a number)

Example

A simple function that writes my name when it is called:

<html>
<body>

<?php
function writeName()
{
echo “Kai Jim Refsnes”;
}

echo “My name is “;
writeName();
?>

</body>
</html>

Output:

My name is Kai Jim Refsnes

PHP Functions – Adding parameters

To add more functionality to a function, we can add parameters. A parameter is just like a variable.

Parameters are specified after the function name, inside the parentheses.

Example 1

The following example will write different first names, but equal last name:

<html>
<body>

<?php
function writeName($fname)
{
echo $fname . ” Refsnes.<br />”;
}

echo “My name is “;
writeName(“Kai Jim”);
echo “My sister’s name is “;
writeName(“Hege”);
echo “My brother’s name is “;
writeName(“Stale”);
?>

</body>
</html>

Output:

My name is Kai Jim Refsnes.
My sister’s name is Hege Refsnes.
My brother’s name is Stale Refsnes.

Example 2

The following function has two parameters:

<html>
<body>

<?php
function writeName($fname,$punctuation)
{
echo $fname . ” Refsnes” . $punctuation . “<br />”;
}

echo “My name is “;
writeName(“Kai Jim”,”.”);
echo “My sister’s name is “;
writeName(“Hege”,”!”);
echo “My brother’s name is “;
writeName(“Ståle”,”?”);
?>

</body>
</html>

Output:

My name is Kai Jim Refsnes.
My sister’s name is Hege Refsnes!
My brother’s name is Ståle Refsnes?

 


PHP Functions – Return values

To let a function return a value, use the return statement.

Example

<html>
<body>

<?php
function add($x,$y)
{
$total=$x+$y;
return $total;
}

echo “1 + 16 = ” . add(1,16);
?>

</body>
</html>

Output:

1 + 16 = 17

PHP Forms and User Input



The PHP $_GET and $_POST variables are used to retrieve information from forms, like user input.


PHP Form Handling

The most important thing to notice when dealing with HTML forms and PHP is that any form element in an HTML page will automatically be available to your PHP scripts.

Example

The example below contains an HTML form with two input fields and a submit button:

<html>
<body>

<form action=”welcome.php” method=”post”>
Name: <input type=”text” name=”fname” />
Age: <input type=”text” name=”age” />
<input type=”submit” />
</form>

</body>
</html>

When a user fills out the form above and click on the submit button, the form data is sent to a PHP file, called “welcome.php”:

“welcome.php” looks like this:

<html>
<body>

Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.

</body>
</html>

Output could be something like this:

Welcome John!
You are 28 years old.

The PHP $_GET and $_POST functions will be explained in the next chapters.


Form Validation

User input should be validated on the browser whenever possible (by client scripts). Browser validation is faster and reduces the server load.

You should consider server validation if the user input will be inserted into a database. A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error.


PHP $_GET Function



The built-in $_GET function is used to collect values in a form with method=”get”.


The $_GET Function

The built-in $_GET function is used to collect values from a form sent with method=”get”.

Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser’s address bar) and has limits on the amount of information to send (max. 100 characters).

Example

<form action=”welcome.php” method=”get”>
Name: <input type=”text” name=”fname” />
Age: <input type=”text” name=”age” />
<input type=”submit” />
</form>

When the user clicks the “Submit” button, the URL sent to the server could look something like this:

http://www.w3schools.com/welcome.php?fname=Peter&age=37

The “welcome.php” file can now use the $_GET function to collect form data (the names of the form fields will automatically be the keys in the $_GET array):

Welcome <?php echo $_GET["fname"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!

When to use method=”get”?

When using method=”get” in HTML forms, all variable names and values are displayed in the URL.

Note: This method should not be used when sending passwords or other sensitive information!

However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.

Note: The get method is not suitable for large variable values; the value cannot exceed 100 characters.


PHP $_POST Function



The built-in $_POST function is used to collect values in a form with method=”post”.


The $_POST Function

The built-in $_POST function is used to collect values from a form sent with method=”post”.

Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

Note: However, there is an 8 Mb max size for the POST method, by default (can be changed by setting the post_max_size in the php.ini file).

Example

<form action=”welcome.php” method=”post”>
Name: <input type=”text” name=”fname” />
Age: <input type=”text” name=”age” />
<input type=”submit” />
</form>

When the user clicks the “Submit” button, the URL will look like this:

http://www.w3schools.com/welcome.php

The “welcome.php” file can now use the $_POST function to collect form data (the names of the form fields will automatically be the keys in the $_POST array):

Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.

When to use method=”post”?

Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

However, because the variables are not displayed in the URL, it is not possible to bookmark the page.


The PHP $_REQUEST Function

The PHP built-in $_REQUEST function contains the contents of both $_GET, $_POST, and $_COOKIE.

The $_REQUEST function can be used to collect form data sent with both the GET and POST methods.

Example

Welcome <?php echo $_REQUEST["fname"]; ?>!<br />
You are <?php echo $_REQUEST["age"]; ?> years old.

PHP Date() Function



The PHP date() function is used to format a time and/or date.


The PHP Date() Function

The PHP date() function formats a timestamp to a more readable date and time.

A timestamp is a sequence of characters, denoting the date and/or time at which a certain event occurred.

Syntax

date(format,timestamp)
Parameter Description
format Required. Specifies the format of the timestamp
timestamp Optional. Specifies a timestamp. Default is the current date and time

PHP Date() – Format the Date

The required format parameter in the date() function specifies how to format the date/time.

Here are some characters that can be used:

  • d – Represents the day of the month (01 to 31)
  • m – Represents a month (01 to 12)
  • Y – Represents a year (in four digits)

A list of all the characters that can be used in the format parameter, can be found in our PHP Date reference.

Other characters, like”/”, “.”, or “-” can also be inserted between the letters to add additional formatting:

<?php
echo date(“Y/m/d”) . “<br />”;
echo date(“Y.m.d”) . “<br />”;
echo date(“Y-m-d”)
?>

The output of the code above could be something like this:

2009/05/11
2009.05.11
2009-05-11

PHP Date() – Adding a Timestamp

The optional timestamp parameter in the date() function specifies a timestamp. If you do not specify a timestamp, the current date and time will be used.

The mktime() function returns the Unix timestamp for a date.

The Unix timestamp contains the number of seconds between the Unix Epoch (January 1 1970 00:00:00 GMT) and the time specified.

Syntax for mktime()

mktime(hour,minute,second,month,day,year,is_dst)

To go one day in the future we simply add one to the day argument of mktime():

<?php
$tomorrow = mktime(0,0,0,date(“m”),date(“d”)+1,date(“Y”));
echo “Tomorrow is “.date(“Y/m/d”, $tomorrow);
?>

The output of the code above could be something like this:

Tomorrow is 2009/05/12

PHP Date – Reference

For more information about all the built-in PHP date functions, please visit our PHP Date Reference.


PHP Include File



Server Side Includes (SSI)

You can insert the content of one PHP file into another PHP file before the server executes it, with the include() or require() function.

The two functions are identical in every way, except how they handle errors:

  • include() generates a warning, but the script will continue execution
  • require() generates a fatal error, and the script will stop

These two functions are used to create functions, headers, footers, or elements that will be reused on multiple pages.

Server side includes saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. When the header needs to be updated, you can only update the include file, or when you add a new page to your site, you can simply change the menu file (instead of updating the links on all your web pages).


PHP include() Function

The include() function takes all the content in a specified file and includes it in the current file.

If an error occurs, the include() function generates a warning, but the script will continue execution.

Example 1

Assume that you have a standard header file, called “header.php”. To include the header file in a page, use the include() function:

<html>
<body>

<?php include(“header.php”); ?>
<h1>Welcome to my home page!</h1>
<p>Some text.</p>

</body>
</html>

Example 2

Assume we have a standard menu file, called “menu.php”, that should be used on all pages:

<a href=”/default.php”>Home</a>
<a href=”/tutorials.php”>Tutorials</a>
<a href=”/references.php”>References</a>
<a href=”/examples.php”>Examples</a>
<a href=”/about.php”>About Us</a>
<a href=”/contact.php”>Contact Us</a>

All pages in the Web site should include this menu file. Here is how it can be done:

<html>
<body>

<div>
<?php include(“menu.php”); ?>
</div>

<h1>Welcome to my home page.</h1>
<p>Some text.</p>

</body>
</html>

If you look at the source code of the page above (in a browser), it will look like this:

<html>
<body>

<div>
<a href=”/default.php”>Home</a>
<a href=”/tutorials.php”>Tutorials</a>
<a href=”/references.php”>References</a>
<a href=”/examples.php”>Examples</a>
<a href=”/about.php”>About Us</a>
<a href=”/contact.php”>Contact Us</a>
</div>

<h1>Welcome to my home page!</h1>
<p>Some text.</p>

</body>
</html>


PHP require() Function

The require() function is identical to include(), except that it handles errors differently.

If an error occurs, the include() function generates a warning, but the script will continue execution. The require() generates a fatal error, and the script will stop.

Error Example include() Function

<html>
<body>

<?php
include(“wrongFile.php”);
echo “Hello World!”;
?>

</body>
</html>

Error message:

Warning: include(wrongFile.php) [function.include]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5

Warning: include() [function.include]:
Failed opening ‘wrongFile.php’ for inclusion
(include_path=’.;C:\php5\pear’)
in C:\home\website\test.php on line 5

Hello World!

Notice that the echo statement is executed! This is because a Warning does not stop the script execution.

Error Example require() Function

Now, let’s run the same example with the require() function.

<html>
<body>

<?php
require(“wrongFile.php”);
echo “Hello World!”;
?>

</body>
</html>

Error message:

Warning: require(wrongFile.php) [function.require]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5

Fatal error: require() [function.require]:
Failed opening required ‘wrongFile.php’
(include_path=’.;C:\php5\pear’)
in C:\home\website\test.php on line 5

The echo statement is not executed, because the script execution stopped after the fatal error.

It is recommended to use the require() function instead of include(), because scripts should not continue after an error.


PHP File Handling



The fopen() function is used to open files in PHP.


Opening a File

The fopen() function is used to open files in PHP.

The first parameter of this function contains the name of the file to be opened and the second parameter specifies in which mode the file should be opened:

<html>
<body>

<?php
$file=fopen(“welcome.txt”,”r”);
?>

</body>
</html>

The file may be opened in one of the following modes:

Modes Description
r Read only. Starts at the beginning of the file
r+ Read/Write. Starts at the beginning of the file
w Write only. Opens and clears the contents of file; or creates a new file if it doesn’t exist
w+ Read/Write. Opens and clears the contents of file; or creates a new file if it doesn’t exist
a Append. Opens and writes to the end of the file or creates a new file if it doesn’t exist
a+ Read/Append. Preserves file content by writing to the end of the file
x Write only. Creates a new file. Returns FALSE and an error if file already exists
x+ Read/Write. Creates a new file. Returns FALSE and an error if file already exists

Note: If the fopen() function is unable to open the specified file, it returns 0 (false).

Example

The following example generates a message if the fopen() function is unable to open the specified file:

<html>
<body>

<?php
$file=fopen(“welcome.txt”,”r”) or exit(“Unable to open file!”);
?>

</body>
</html>


Closing a File

The fclose() function is used to close an open file:

<?php
$file = fopen(“test.txt”,”r”);

//some code to be executed

fclose($file);
?>


Check End-of-file

The feof() function checks if the “end-of-file” (EOF) has been reached.

The feof() function is useful for looping through data of unknown length.

Note: You cannot read from files opened in w, a, and x mode!

if (feof($file)) echo “End of file”;

Reading a File Line by Line

The fgets() function is used to read a single line from a file.

Note: After a call to this function the file pointer has moved to the next line.

Example

The example below reads a file line by line, until the end of file is reached:

<?php
$file = fopen(“welcome.txt”, “r”) or exit(“Unable to open file!”);
//Output a line of the file until the end is reached
while(!feof($file))
   {
   echo fgets($file). “<br />”;
   }
fclose($file);
?>

Reading a File Character by Character

The fgetc() function is used to read a single character from a file.

Note: After a call to this function the file pointer moves to the next character.

Example

The example below reads a file character by character, until the end of file is reached:

<?php
$file=fopen(“welcome.txt”,”r”) or exit(“Unable to open file!”);
while (!feof($file))
   {
   echo fgetc($file);
   }
fclose($file);
?>

PHP Filesystem Reference

For a full reference of the PHP filesystem functions, visit our PHP Filesystem Reference.


PHP File Upload



With PHP, it is possible to upload files to the server.


Create an Upload-File Form

To allow users to upload files from a form can be very useful.

Look at the following HTML form for uploading files:

<html>
<body>

<form action=”upload_file.php” method=”post”
enctype=”multipart/form-data”>
<label for=”file”>Filename:</label>
<input type=”file” name=”file” id=”file” />
<br />
<input type=”submit” name=”submit” value=”Submit” />
</form>

</body>
</html>

Notice the following about the HTML form above:

  • The enctype attribute of the <form> tag specifies which content-type to use when submitting the form. “multipart/form-data” is used when a form requires binary data, like the contents of a file, to be uploaded
  • The type=”file” attribute of the <input> tag specifies that the input should be processed as a file. For example, when viewed in a browser, there will be a browse-button next to the input field

Note: Allowing users to upload files is a big security risk. Only permit trusted users to perform file uploads.


Create The Upload Script

The “upload_file.php” file contains the code for uploading a file:

<?php
if ($_FILES["file"]["error"] > 0)
   {
   echo “Error: ” . $_FILES["file"]["error"] . “<br />”;
   }
else
   {
   echo “Upload: ” . $_FILES["file"]["name"] . “<br />”;
   echo “Type: ” . $_FILES["file"]["type"] . “<br />”;
   echo “Size: ” . ($_FILES["file"]["size"] / 1024) . ” Kb<br />”;
   echo “Stored in: ” . $_FILES["file"]["tmp_name"];
   }
?>

By using the global PHP $_FILES array you can upload files from a client computer to the remote server.

The first parameter is the form’s input name and the second index can be either “name”, “type”, “size”, “tmp_name” or “error”. Like this:

  • $_FILES["file"]["name"] – the name of the uploaded file
  • $_FILES["file"]["type"] – the type of the uploaded file
  • $_FILES["file"]["size"] – the size in bytes of the uploaded file
  • $_FILES["file"]["tmp_name"] – the name of the temporary copy of the file stored on the server
  • $_FILES["file"]["error"] – the error code resulting from the file upload

This is a very simple way of uploading files. For security reasons, you should add restrictions on what the user is allowed to upload.


Restrictions on Upload

In this script we add some restrictions to the file upload. The user may only upload .gif or .jpeg files and the file size must be under 20 kb:

<?php
if ((($_FILES["file"]["type"] == “image/gif”)
|| ($_FILES["file"]["type"] == “image/jpeg”)
|| ($_FILES["file"]["type"] == “image/pjpeg”))
&& ($_FILES["file"]["size"] < 20000))
   {
   if ($_FILES["file"]["error"] > 0)
     {
     echo “Error: ” . $_FILES["file"]["error"] . “<br />”;
     }
   else
     {
     echo “Upload: ” . $_FILES["file"]["name"] . “<br />”;
     echo “Type: ” . $_FILES["file"]["type"] . “<br />”;
     echo “Size: ” . ($_FILES["file"]["size"] / 1024) . ” Kb<br />”;
     echo “Stored in: ” . $_FILES["file"]["tmp_name"];
     }
   }
else
   {
   echo “Invalid file”;
   }
?>

Note: For IE to recognize jpg files the type must be pjpeg, for FireFox it must be jpeg.


Saving the Uploaded File

The examples above create a temporary copy of the uploaded files in the PHP temp folder on the server.

The temporary copied files disappears when the script ends. To store the uploaded file we need to copy it to a different location:

<?php
if ((($_FILES["file"]["type"] == “image/gif”)
|| ($_FILES["file"]["type"] == “image/jpeg”)
|| ($_FILES["file"]["type"] == “image/pjpeg”))
&& ($_FILES["file"]["size"] < 20000))
   {
   if ($_FILES["file"]["error"] > 0)
     {
     echo “Return Code: ” . $_FILES["file"]["error"] . “<br />”;
     }
   else
     {
     echo “Upload: ” . $_FILES["file"]["name"] . “<br />”;
     echo “Type: ” . $_FILES["file"]["type"] . “<br />”;
     echo “Size: ” . ($_FILES["file"]["size"] / 1024) . ” Kb<br />”;
     echo “Temp file: ” . $_FILES["file"]["tmp_name"] . “<br />”;

     if (file_exists(“upload/” . $_FILES["file"]["name"]))
       {
       echo $_FILES["file"]["name"] . ” already exists. “;
       }
     else
       {
       move_uploaded_file($_FILES["file"]["tmp_name"],
       “upload/” . $_FILES["file"]["name"]);
       echo “Stored in: ” . “upload/” . $_FILES["file"]["name"];
       }
     }
   }
else
   {
   echo “Invalid file”;
   }
?>

The script above checks if the file already exists, if it does not, it copies the file to the specified folder.

Note: This example saves the file to a new folder called “upload”


PHP Cookies



A cookie is often used to identify a user.


What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user’s computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.


How to Create a Cookie?

The setcookie() function is used to set a cookie.

Note: The setcookie() function must appear BEFORE the <html> tag.

Syntax

setcookie(name, value, expire, path, domain);

Example 1

In the example below, we will create a cookie named “user” and assign the value “Alex Porter” to it. We also specify that the cookie should expire after one hour:

<?php
setcookie(“user”, “Alex Porter”, time()+3600);
?>

<html>
…..

Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received (to prevent URLencoding, use setrawcookie() instead).

Example 2

You can also set the expiration time of the cookie in another way. It may be easier than using seconds.

<?php
$expire=time()+60*60*24*30;
setcookie(“user”, “Alex Porter”, $expire);
?>

<html>
…..

In the example above the expiration time is set to a month (60 sec * 60 min * 24 hours * 30 days).


How to Retrieve a Cookie Value?

The PHP $_COOKIE variable is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named “user” and display it on a page:

<?php
// Print a cookie
echo $_COOKIE["user"];

// A way to view all cookies
print_r($_COOKIE);
?>

In the following example we use the isset() function to find out if a cookie has been set:

<html>
<body>

<?php
if (isset($_COOKIE["user"]))
   echo “Welcome ” . $_COOKIE["user"] . “!<br />”;
else
   echo “Welcome guest!<br />”;
?>

</body>
</html>


How to Delete a Cookie?

When deleting a cookie you should assure that the expiration date is in the past.

Delete example:

<?php
// set the expiration date to one hour ago
setcookie(“user”, “”, time()-3600);
?>

What if a Browser Does NOT Support Cookies?

If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms (forms and user input are described earlier in this tutorial).

The form below passes the user input to “welcome.php” when the user clicks on the “Submit” button:

<html>
<body>

<form action=”welcome.php” method=”post”>
Name: <input type=”text” name=”name” />
Age: <input type=”text” name=”age” />
<input type=”submit” />
</form>

</body>
</html>

Retrieve the values in the “welcome.php” file like this:

<html>
<body>

Welcome <?php echo $_POST["name"]; ?>.<br />
You are <?php echo $_POST["age"]; ?> years old.

</body>
</html>


PHP Sessions



A PHP session variable is used to store information about, or change settings for a user session. Session variables hold information about one single user, and are available to all pages in one application.


PHP Session Variables

When you are working with an application, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn’t maintain state.

A PHP session solves this problem by allowing you to store user information on the server for later use (i.e. username, shopping items, etc). However, session information is temporary and will be deleted after the user has left the website. If you need a permanent storage you may want to store the data in a database.

Sessions work by creating a unique id (UID) for each visitor and store variables based on this UID. The UID is either stored in a cookie or is propagated in the URL.


Starting a PHP Session

Before you can store user information in your PHP session, you must first start up the session.

Note: The session_start() function must appear BEFORE the <html> tag:

<?php session_start(); ?>

<html>
<body>

</body>
</html>

The code above will register the user’s session with the server, allow you to start saving user information, and assign a UID for that user’s session.


Storing a Session Variable

The correct way to store and retrieve session variables is to use the PHP $_SESSION variable:

<?php
session_start();
// store session data
$_SESSION['views']=1;
?>

<html>
<body>

<?php
//retrieve session data
echo “Pageviews=”. $_SESSION['views'];
?>

</body>
</html>

Output:

Pageviews=1

In the example below, we create a simple page-views counter. The isset() function checks if the “views” variable has already been set. If “views” has been set, we can increment our counter. If “views” doesn’t exist, we create a “views” variable, and set it to 1:

<?php
session_start();

if(isset($_SESSION['views']))
$_SESSION['views']=$_SESSION['views']+1;
else
$_SESSION['views']=1;
echo “Views=”. $_SESSION['views'];
?>


Destroying a Session

If you wish to delete some session data, you can use the unset() or the session_destroy() function.

The unset() function is used to free the specified session variable:

<?php
unset($_SESSION['views']);
?>

You can also completely destroy the session by calling the session_destroy() function:

<?php
session_destroy();
?>

Note: session_destroy() will reset your session and you will lose all your stored session data.


PHP Sending E-mails



PHP allows you to send e-mails directly from a script.


The PHP mail() Function

The PHP mail() function is used to send emails from inside a script.

Syntax

mail(to,subject,message,headers,parameters)
Parameter Description
to Required. Specifies the receiver / receivers of the email
subject Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters
message Required. Defines the message to be sent. Each line should be separated with a LF (\n). Lines should not exceed 70 characters
headers Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)
parameters Optional. Specifies an additional parameter to the sendmail program

Note: For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file. Read more in our PHP Mail reference.


PHP Simple E-Mail

The simplest way to send an email with PHP is to send a text email.

In the example below we first declare the variables ($to, $subject, $message, $from, $headers), then we use the variables in the mail() function to send an e-mail:

<?php
$to = “someone@example.com”;
$subject = “Test mail”;
$message = “Hello! This is a simple email message.”;
$from = “someonelse@example.com”;
$headers = “From: $from”;
mail($to,$subject,$message,$headers);
echo “Mail Sent.”;
?>

PHP Mail Form

With PHP, you can create a feedback-form on your website. The example below sends a text message to a specified e-mail address:

<html>
<body>

<?php
if (isset($_REQUEST['email']))
//if “email” is filled out, send email
   {
   //send email
   $email = $_REQUEST['email'] ;
   $subject = $_REQUEST['subject'] ;
   $message = $_REQUEST['message'] ;
   mail( “someone@example.com”, “Subject: $subject”,
   $message, “From: $email” );
   echo “Thank you for using our mail form”;
   }
else
//if “email” is not filled out, display the form
   {
   echo “<form method=’post’ action=’mailform.php’>
   Email: <input name=’email’ type=’text’ /><br />
   Subject: <input name=’subject’ type=’text’ /><br />
   Message:<br />
   <textarea name=’message’ rows=’15′ cols=’40′>
   </textarea><br />
   <input type=’submit’ />
   </form>”;
   }
?>

</body>
</html>

This is how the example above works:

  • First, check if the email input field is filled out
  • If it is not set (like when the page is first visited); output the HTML form
  • If it is set (after the form is filled out); send the email from the form
  • When submit is pressed after the form is filled out, the page reloads, sees that the email input is set, and sends the email

Note: This is the simplest way to send e-mail, but it is not secure. In the next chapter of this tutorial you can read more about vulnerabilities in e-mail scripts, and how to validate user input to make it more secure.


PHP Mail Reference

For more information about the PHP mail() function, visit our PHP Mail Reference.


PHP Secure E-mails



There is a weakness in the PHP e-mail script in the previous chapter.


PHP E-mail Injections

First, look at the PHP code from the previous chapter:

<html>
<body>

<?php
if (isset($_REQUEST['email']))
//if “email” is filled out, send email
   {
   //send email
   $email = $_REQUEST['email'] ;
   $subject = $_REQUEST['subject'] ;
   $message = $_REQUEST['message'] ;
   mail(“someone@example.com”, “Subject: $subject”,
   $message, “From: $email” );
   echo “Thank you for using our mail form”;
   }
else
//if “email” is not filled out, display the form
   {
   echo “<form method=’post’ action=’mailform.php’>
   Email: <input name=’email’ type=’text’ /><br />
   Subject: <input name=’subject’ type=’text’ /><br />
   Message:<br />
   <textarea name=’message’ rows=’15′ cols=’40′>
   </textarea><br />
   <input type=’submit’ />
   </form>”;
   }
?>

</body>
</html>

The problem with the code above is that unauthorized users can insert data into the mail headers via the input form.

What happens if the user adds the following text to the email input field in the form?

someone@example.com%0ACc:person2@example.com
%0ABcc:person3@example.com,person3@example.com,
anotherperson4@example.com,person5@example.com
%0ABTo:person6@example.com

The mail() function puts the text above into the mail headers as usual, and now the header has an extra Cc:, Bcc:, and To: field. When the user clicks the submit button, the e-mail will be sent to all of the addresses above!


PHP Stopping E-mail Injections

The best way to stop e-mail injections is to validate the input.

The code below is the same as in the previous chapter, but now we have added an input validator that checks the email field in the form:

<html>
<body>
<?php
function spamcheck($field)
   {
   //filter_var() sanitizes the e-mail
   //address using FILTER_SANITIZE_EMAIL
   $field=filter_var($field, FILTER_SANITIZE_EMAIL);

   //filter_var() validates the e-mail
   //address using FILTER_VALIDATE_EMAIL
   if(filter_var($field, FILTER_VALIDATE_EMAIL))
     {
     return TRUE;
     }
   else
     {
     return FALSE;
     }
   }

if (isset($_REQUEST['email']))
   {//if “email” is filled out, proceed

   //check if the email address is invalid
   $mailcheck = spamcheck($_REQUEST['email']);
   if ($mailcheck==FALSE)
     {
     echo “Invalid input”;
     }
   else
     {//send email
     $email = $_REQUEST['email'] ;
     $subject = $_REQUEST['subject'] ;
     $message = $_REQUEST['message'] ;
     mail(“someone@example.com”, “Subject: $subject”,
     $message, “From: $email” );
     echo “Thank you for using our mail form”;
     }
   }
else
   {//if “email” is not filled out, display the form
   echo “<form method=’post’ action=’mailform.php’>
   Email: <input name=’email’ type=’text’ /><br />
   Subject: <input name=’subject’ type=’text’ /><br />
   Message:<br />
   <textarea name=’message’ rows=’15′ cols=’40′>
   </textarea><br />
   <input type=’submit’ />
   </form>”;
   }
?>

</body>
</html>

In the code above we use PHP filters to validate input:

  • The FILTER_SANITIZE_EMAIL filter removes all illegal e-mail characters from a string
  • The FILTER_VALIDATE_EMAIL filter validates value as an e-mail address

You can read more about filters in our PHP Filter chapter.


PHP Error Handling



The default error handling in PHP is very simple. An error message with filename, line number and a message describing the error is sent to the browser.


PHP Error Handling

When creating scripts and web applications, error handling is an important part. If your code lacks error checking code, your program may look very unprofessional and you may be open to security risks.

This tutorial contains some of the most common error checking methods in PHP.

We will show different error handling methods:

  • Simple “die()” statements
  • Custom errors and error triggers
  • Error reporting

Basic Error Handling: Using the die() function

The first example shows a simple script that opens a text file:

<?php
$file=fopen(“welcome.txt”,”r”);
?>

If the file does not exist you might get an error like this:

Warning: fopen(welcome.txt) [function.fopen]: failed to open stream:
No such file or directory in C:\webfolder\test.php on line 2

To avoid that the user gets an error message like the one above, we test if the file exist before we try to access it:

<?php
if(!file_exists(“welcome.txt”))
   {
   die(“File not found”);
   }
else
   {
   $file=fopen(“welcome.txt”,”r”);
   }
?>

Now if the file does not exist you get an error like this:

File not found

The code above is more efficient than the earlier code, because it uses a simple error handling mechanism to stop the script after the error.

However, simply stopping the script is not always the right way to go. Let’s take a look at alternative PHP functions for handling errors.


Creating a Custom Error Handler

Creating a custom error handler is quite simple. We simply create a special function that can be called when an error occurs in PHP.

This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):

Syntax

error_function(error_level,error_message,
error_file,error_line,error_context)
Parameter Description
error_level Required. Specifies the error report level for the user-defined error. Must be a value number. See table below for possible error report levels
error_message Required. Specifies the error message for the user-defined error
error_file Optional. Specifies the filename in which the error occurred
error_line Optional. Specifies the line number in which the error occurred
error_context Optional. Specifies an array containing every variable, and their values, in use when the error occurred

Error Report levels

These error report levels are the different types of error the user-defined error handler can be used for:

Value Constant Description
2 E_WARNING Non-fatal run-time errors. Execution of the script is not halted
8 E_NOTICE Run-time notices. The script found something that might be an error, but could also happen when running a script normally
256 E_USER_ERROR Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()
512 E_USER_WARNING Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()
1024 E_USER_NOTICE User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()
4096 E_RECOVERABLE_ERROR Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())
8191 E_ALL All errors and warnings, except level E_STRICT (E_STRICT will be part of E_ALL as of PHP 6.0)

Now lets create a function to handle errors:

function customError($errno, $errstr)
   {
   echo “<b>Error:</b> [$errno] $errstr<br />”;
   echo “Ending Script”;
   die();
   }

The code above is a simple error handling function. When it is triggered, it gets the error level and an error message. It then outputs the error level and message and terminates the script.

Now that we have created an error handling function we need to decide when it should be triggered.


Set Error Handler

The default error handler for PHP is the built in error handler. We are going to make the function above the default error handler for the duration of the script.

It is possible to change the error handler to apply for only some errors, that way the script can handle different errors in different ways. However, in this example we are going to use our custom error handler for all errors:

set_error_handler(“customError”);

Since we want our custom function to handle all errors, the set_error_handler() only needed one parameter, a second parameter could be added to specify an error level.

Example

Testing the error handler by trying to output variable that does not exist:

<?php
//error handler function
function customError($errno, $errstr)
   {
   echo “<b>Error:</b> [$errno] $errstr”;
   }

//set error handler
set_error_handler(“customError”);

//trigger error
echo($test);
?>

The output of the code above should be something like this:

Error: [8] Undefined variable: test

Trigger an Error

In a script where users can input data it is useful to trigger errors when an illegal input occurs. In PHP, this is done by the trigger_error() function.

Example

In this example an error occurs if the “test” variable is bigger than “1″:

<?php
$test=2;
if ($test>1)
{
trigger_error(“Value must be 1 or below”);
}
?>

The output of the code above should be something like this:

Notice: Value must be 1 or below
in C:\webfolder\test.php on line 6

An error can be triggered anywhere you wish in a script, and by adding a second parameter, you can specify what error level is triggered.

Possible error types:

  • E_USER_ERROR – Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halted
  • E_USER_WARNING – Non-fatal user-generated run-time warning. Execution of the script is not halted
  • E_USER_NOTICE – Default. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally

Example

In this example an E_USER_WARNING occurs if the “test” variable is bigger than “1″. If an E_USER_WARNING occurs we will use our custom error handler and end the script:

<?php
//error handler function
function customError($errno, $errstr)
   {
   echo “<b>Error:</b> [$errno] $errstr<br />”;
   echo “Ending Script”;
   die();
   }

//set error handler
set_error_handler(“customError”,E_USER_WARNING);

//trigger error
$test=2;
if ($test>1)
   {
   trigger_error(“Value must be 1 or below”,E_USER_WARNING);
   }
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below
Ending Script

Now that we have learned to create our own errors and how to trigger them, lets take a look at error logging.


Error Logging

By default, PHP sends an error log to the servers logging system or a file, depending on how the error_log configuration is set in the php.ini file. By using the error_log() function you can send error logs to a specified file or a remote destination.

Sending errors messages to yourself by e-mail can be a good way of getting notified of specific errors.

Send an Error Message by E-Mail

In the example below we will send an e-mail with an error message and end the script, if a specific error occurs:

<?php
//error handler function
function customError($errno, $errstr)
   {
   echo “<b>Error:</b> [$errno] $errstr<br />”;
   echo “Webmaster has been notified”;
   error_log(“Error: [$errno] $errstr”,1,
   “someone@example.com”,”From: webmaster@example.com”);
   }

//set error handler
set_error_handler(“customError”,E_USER_WARNING);

//trigger error
$test=2;
if ($test>1)
   {
   trigger_error(“Value must be 1 or below”,E_USER_WARNING);
   }
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below
Webmaster has been notified

And the mail received from the code above looks like this:

Error: [512] Value must be 1 or below

This should not be used with all errors. Regular errors should be logged on the server using the default PHP logging system.


PHP Exception Handling



Exceptions are used to change the normal flow of a script if a specified error occurs


What is an Exception

With PHP 5 came a new object oriented way of dealing with errors.

Exception handling is used to change the normal flow of the code execution if a specified error (exceptional) condition occurs. This condition is called an exception.

This is what normally happens when an exception is triggered:

  • The current code state is saved
  • The code execution will switch to a predefined (custom) exception handler function
  • Depending on the situation, the handler may then resume the execution from the saved code state, terminate the script execution or continue the script from a different location in the code

We will show different error handling methods:

  • Basic use of Exceptions
  • Creating a custom exception handler
  • Multiple exceptions
  • Re-throwing an exception
  • Setting a top level exception handler

Note: Exceptions should only be used with error conditions, and should not be used to jump to another place in the code at a specified point.


Basic Use of Exceptions

When an exception is thrown, the code following it will not be executed, and PHP will try to find the matching “catch” block.

If an exception is not caught, a fatal error will be issued with an “Uncaught Exception” message.

Lets try to throw an exception without catching it:

<?php
//create function with an exception
function checkNum($number)
   {
   if($number>1)
     {
     throw new Exception(“Value must be 1 or below”);
     }
   return true;
   }

//trigger exception
checkNum(2);
?>

The code above will get an error like this:

Fatal error: Uncaught exception ‘Exception’
with message ‘Value must be 1 or below’ in C:\webfolder\test.php:6
Stack trace: #0 C:\webfolder\test.php(12):
checkNum(28) #1 {main} thrown in C:\webfolder\test.php on line 6

Try, throw and catch

To avoid the error from the example above, we need to create the proper code to handle an exception.

Proper exception code should include:

  1. Try – A function using an exception should be in a “try” block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is “thrown”
  2. Throw – This is how you trigger an exception. Each “throw” must have at least one “catch”
  3. Catch – A “catch” block retrieves an exception and creates an object containing the exception information

Lets try to trigger an exception with valid code:

<?php
//create function with an exception
function checkNum($number)
   {
   if($number>1)
     {
     throw new Exception(“Value must be 1 or below”);
     }
   return true;
   }

//trigger exception in a “try” block
try
   {
   checkNum(2);
   //If the exception is thrown, this text will not be shown
   echo ‘If you see this, the number is 1 or below’;
   }

//catch exception
catch(Exception $e)
   {
   echo ‘Message: ‘ .$e->getMessage();
   }
?>

The code above will get an error like this:

Message: Value must be 1 or below

Example explained:

The code above throws an exception and catches it:

  1. The checkNum() function is created. It checks if a number is greater than 1. If it is, an exception is thrown
  2. The checkNum() function is called in a “try” block
  3. The exception within the checkNum() function is thrown
  4. The “catch” block retrives the exception and creates an object ($e) containing the exception information
  5. The error message from the exception is echoed by calling $e->getMessage() from the exception object

However, one way to get around the “every throw must have a catch” rule is to set a top level exception handler to handle errors that slip through.


Creating a Custom Exception Class

Creating a custom exception handler is quite simple. We simply create a special class with functions that can be called when an exception occurs in PHP. The class must be an extension of the exception class.

The custom exception class inherits the properties from PHP’s exception class and you can add custom functions to it.

Lets create an exception class:

<?php
class customException extends Exception
   {
   public function errorMessage()
     {
     //error message
     $errorMsg = ‘Error on line ‘.$this->getLine().’ in ‘.$this->getFile()
     .’: <b>’.$this->getMessage().’</b> is not a valid E-Mail address’;
     return $errorMsg;
     }
   }

$email = “someone@example…com”;

try
   {
   //check if
   if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
     {
     //throw exception if email is not valid
     throw new customException($email);
     }
   }

catch (customException $e)
   {
   //display custom message
   echo $e->errorMessage();
   }
?>

The new class is a copy of the old exception class with an addition of the errorMessage() function. Since it is a copy of the old class, and it inherits the properties and methods from the old class, we can use the exception class methods like getLine() and getFile() and getMessage().

Example explained:

The code above throws an exception and catches it with a custom exception class:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is not a valid e-mail address
  4. The “try” block is executed and an exception is thrown since the e-mail address is invalid
  5. The “catch” block catches the exception and displays the error message

Multiple Exceptions

It is possible for a script to use multiple exceptions to check for multiple conditions.

It is possible to use several if..else blocks, a switch, or nest multiple exceptions. These exceptions can use different exception classes and return different error messages:

<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = ‘Error on line ‘.$this->getLine().’ in ‘.$this->getFile()
.’: <b>’.$this->getMessage().’</b> is not a valid E-Mail address’;
return $errorMsg;
}
}

$email = “someone@example.com”;

try
   {
   //check if
   if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
     {
     //throw exception if email is not valid
     throw new customException($email);
     }
   //check for “example” in mail address
   if(strpos($email, “example”) !== FALSE)
     {
     throw new Exception(“$email is an example e-mail”);
     }
   }

catch (customException $e)
   {
   echo $e->errorMessage();
   }

catch(Exception $e)
   {
   echo $e->getMessage();
   }
?>

Example explained:

The code above tests two conditions and throws an exception if any of the conditions are not met:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is a valid e-mail address, but contains the string “example”
  4. The “try” block is executed and an exception is not thrown on the first condition
  5. The second condition triggers an exception since the e-mail contains the string “example”
  6. The “catch” block catches the exception and displays the correct error message

If there was no customException catch, only the base exception catch, the exception would be handled there


Re-throwing Exceptions

Sometimes, when an exception is thrown, you may wish to handle it differently than the standard way. It is possible to throw an exception a second time within a “catch” block.

A script should hide system errors from users. System errors may be important for the coder, but is of no interest to the user. To make things easier for the user you can re-throw the exception with a user friendly message:

<?php
class customException extends Exception
   {
   public function errorMessage()
     {
     //error message
     $errorMsg = $this->getMessage().’ is not a valid E-Mail address.’;
     return $errorMsg;
     }
   }

$email = “someone@example.com”;

try
   {
   try
     {
     //check for “example” in mail address
     if(strpos($email, “example”) !== FALSE)
       {
       //throw exception if email is not valid
       throw new Exception($email);
       }
     }
   catch(Exception $e)
     {
     //re-throw exception
     throw new customException($email);
     }
   }

catch (customException $e)
   {
   //display custom message
   echo $e->errorMessage();
   }
?>

Example explained:

The code above tests if the email-address contains the string “example” in it, if it does, the exception is re-thrown:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is a valid e-mail address, but contains the string “example”
  4. The “try” block contains another “try” block to make it possible to re-throw the exception
  5. The exception is triggered since the e-mail contains the string “example”
  6. The “catch” block catches the exception and re-throws a “customException”
  7. The “customException” is caught and displays an error message

If the exception is not caught in its current “try” block, it will search for a catch block on “higher levels”.


Set a Top Level Exception Handler

The set_exception_handler() function sets a user-defined function to handle all uncaught exceptions.

<?php
function myException($exception)
{
echo “<b>Exception:</b> ” , $exception->getMessage();
}

set_exception_handler(‘myException’);

throw new Exception(‘Uncaught Exception occurred’);
?>

The output of the code above should be something like this:

Exception: Uncaught Exception occurred

In the code above there was no “catch” block. Instead, the top level exception handler triggered. This function should be used to catch uncaught exceptions.


Rules for exceptions

  • Code may be surrounded in a try block, to help catch potential exceptions
  • Each try block or “throw” must have at least one corresponding catch block
  • Multiple catch blocks can be used to catch different classes of exceptions
  • Exceptions can be thrown (or re-thrown) in a catch block within a try block

A simple rule: If you throw something, you have to catch it.


PHP Filter



PHP filters are used to validate and filter data coming from insecure sources, like user input.


What is a PHP Filter?

A PHP filter is used to validate and filter data coming from insecure sources.

To test, validate and filter user input or custom data is an important part of any web application.

The PHP filter extension is designed to make data filtering easier and quicker.


Why use a Filter?

Almost all web applications depend on external input. Usually this comes from a user or another application (like a web service). By using filters you can be sure your application gets the correct input type.

You should always filter all external data!

Input filtering is one of the most important application security issues.

What is external data?

  • Input data from a form
  • Cookies
  • Web services data
  • Server variables
  • Database query results

Functions and Filters

To filter a variable, use one of the following filter functions:

  • filter_var() – Filters a single variable with a specified filter
  • filter_var_array() – Filter several variables with the same or different filters
  • filter_input – Get one input variable and filter it
  • filter_input_array – Get several input variables and filter them with the same or different filters

In the example below, we validate an integer using the filter_var() function:

<?php
$int = 123;

if(!filter_var($int, FILTER_VALIDATE_INT))
   {
   echo(“Integer is not valid”);
   }
else
   {
   echo(“Integer is valid”);
   }
?>

The code above uses the “FILTER_VALIDATE_INT”  filter to filter the variable. Since the integer is valid, the output of the code above will be: “Integer is valid”.

If we try with a variable that is not an integer (like “123abc”), the output will be: “Integer is not valid”.

For a complete list of functions and filters, visit our PHP Filter Reference.


Validating and Sanitizing

There are two kinds of filters:

Validating filters:

  • Are used to validate user input
  • Strict format rules (like URL or E-Mail validating)
  • Returns the expected type on success or FALSE on failure

Sanitizing filters:

  • Are used to allow or disallow specified characters in a string
  • No data format rules
  • Always return the string

Options and Flags

Options and flags are used to add additional filtering options to the specified filters.

Different filters have different options and flags.

In the example below, we validate an integer using the filter_var() and the “min_range” and “max_range” options:

<?php
$var=300;

$int_options = array(
“options”=>array
   (
   “min_range”=>0,
   “max_range”=>256
   )
);

if(!filter_var($var, FILTER_VALIDATE_INT, $int_options))
   {
   echo(“Integer is not valid”);
   }
else
   {
   echo(“Integer is valid”);
   }
?>

Like the code above, options must be put in an associative array with the name “options”. If a flag is used it does not need to be in an array.

Since the integer is “300″ it is not in the specified range, and the output of the code above will be: “Integer is not valid”.

For a complete list of functions and filters, visit our PHP Filter Reference. Check each filter to see what options and flags are available.


Validate Input

Let’s try validating input from a form.

The first thing we need to do is to confirm that the input data we are looking for exists.

Then we filter the input data using the filter_input() function.

In the example below, the input variable “email” is sent to the PHP page:

<?php
if(!filter_has_var(INPUT_GET, “email”))
   {
   echo(“Input type does not exist”);
   }
else
   {
   if (!filter_input(INPUT_GET, “email”, FILTER_VALIDATE_EMAIL))
     {
     echo “E-Mail is not valid”;
     }
   else
     {
     echo “E-Mail is valid”;
     }
   }
?>

Example Explained

The example above has an input (email) sent to it using the “GET” method:

  1. Check if an “email” input variable of the “GET” type exist
  2. If the input variable exists, check if it is a valid e-mail address

Sanitize Input

Let’s try cleaning up an URL sent from a form.

First we confirm that the input data we are looking for exists.

Then we sanitize the input data using the filter_input() function.

In the example below, the input variable “url” is sent to the PHP page:

<?php
if(!filter_has_var(INPUT_POST, “url”))
   {
   echo(“Input type does not exist”);
   }
else
   {
   $url = filter_input(INPUT_POST,
   “url”, FILTER_SANITIZE_URL);
   }
?>

Example Explained

The example above has an input (url) sent to it using the “POST” method:

  1. Check if the “url” input of the “POST” type exists
  2. If the input variable exists, sanitize (take away invalid characters) and store it in the $url variable

If the input variable is a string like this “http://www.W3ååSchøøools.com/&#8221;, the $url variable after the sanitizing will look like this:

http://www.W3Schools.com/

Filter Multiple Inputs

A form almost always consist of more than one input field. To avoid calling the filter_var or filter_input functions over and over, we can use the filter_var_array or the filter_input_array functions.

In this example we use the filter_input_array() function to filter three GET variables. The received GET variables is a name, an age and an e-mail address:

<?php
$filters = array
   (
   “name” => array
     (
     “filter”=>FILTER_SANITIZE_STRING
     ),
   “age” => array
     (
     “filter”=>FILTER_VALIDATE_INT,
     “options”=>array
       (
       “min_range”=>1,
       “max_range”=>120
       )
     ),
   “email”=> FILTER_VALIDATE_EMAIL,
   );

$result = filter_input_array(INPUT_GET, $filters);

if (!$result["age"])
   {
   echo(“Age must be a number between 1 and 120.<br />”);
   }
elseif(!$result["email"])
   {
   echo(“E-Mail is not valid.<br />”);
   }
else
   {
   echo(“User input is valid”);
   }
?>

Example Explained

The example above has three inputs (name, age and email) sent to it using the “GET” method:

  1. Set an array containing the name of input variables and the filters used on the specified input variables
  2. Call the filter_input_array() function with the GET input variables and the array we just set
  3. Check the “age” and “email” variables in the $result variable for invalid inputs. (If any of the input variables are invalid, that input variable will be FALSE after the filter_input_array() function)

The second parameter of the filter_input_array() function can be an array or a single filter ID.

If the parameter is a single filter ID all values in the input array are filtered by the specified filter.

If the parameter is an array it must follow these rules:

  • Must be an associative array containing an input variable as an array key (like the “age” input variable)
  • The array value must be a filter ID or an array specifying the filter, flags and options

Using Filter Callback

It is possible to call a user defined function and use it as a filter using the FILTER_CALLBACK filter. This way, we have full control of the data filtering.

You can create your own user defined function or use an existing PHP function

The function you wish to use to filter is specified the same way as an option is specified. In an associative array with the name “options”

In the example below, we use a user created function to convert all  “_” to whitespaces:

<?php
function convertSpace($string)
{
return str_replace(“_”, ” “, $string);
}

$string = “Peter_is_a_great_guy!”;

echo filter_var($string, FILTER_CALLBACK,
array(“options”=>”convertSpace”));
?>

The result from the code above should look like this:

Peter is a great guy!

Example Explained

The example above converts all “_” to whitespaces:

  1. Create a function to replace “_” to whitespaces
  2. Call the filter_var() function with the FILTER_CALLBACK filter and an array containing our function

PHP MySQL Introduction



MySQL is the most popular open-source database system.


What is MySQL?

MySQL is a database.

The data in MySQL is stored in database objects called tables.

A table is a collections of related data entries and it consists of columns and rows.

Databases are useful when storing information categorically. A company may have a database with the following tables: “Employees”, “Products”, “Customers” and “Orders”.


Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. “Customers” or “Orders”). Tables contain records (rows) with data.

Below is an example of a table called “Persons”:

LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

The table above contains three records (one for each person) and four columns (LastName, FirstName, Address, and City).


Queries

A query is a question or a request.

With MySQL, we can query a database for specific information and have a recordset returned.

Look at the following query:

SELECT LastName FROM Persons

The query above selects all the data in the “LastName” column from the “Persons” table, and will return a recordset like this:

LastName
Hansen
Svendson
Pettersen

Download MySQL Database

If you don’t have a PHP server with a MySQL Database, you can download MySQL for free here: http://www.mysql.com/downloads/index.html


Facts About MySQL Database

One great thing about MySQL is that it can be scaled down to support embedded database applications. Perhaps it is because of this reputation that many people believe that MySQL can only handle small to medium-sized systems.

The truth is that MySQL is the de-facto standard database for web sites that support huge volumes of both data and end users (like Friendster, Yahoo, Google).

Look at http://www.mysql.com/customers/ for an overview of companies using MySQL.


PHP MySQL Connect to a Database



The free MySQL database is very often used with PHP.


Create a Connection to a MySQL Database

Before you can access data in a database, you must create a connection to the database.

In PHP, this is done with the mysql_connect() function.

Syntax

mysql_connect(servername,username,password);
Parameter Description
servername Optional. Specifies the server to connect to. Default value is “localhost:3306″
username Optional. Specifies the username to log in with. Default value is the name of the user that owns the server process
password Optional. Specifies the password to log in with. Default is “”

Note: There are more available parameters, but the ones listed above are the most important. Visit our full PHP MySQL Reference for more details.

Example

In the following example we store the connection in a variable ($con) for later use in the script. The “die” part will be executed if the connection fails:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

// some code
?>


Closing a Connection

The connection will be closed automatically when the script ends. To close the connection before, use the mysql_close() function:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

// some code

mysql_close($con);
?>


PHP MySQL Create Database and Tables



A database holds one or multiple tables.


Create a Database

The CREATE DATABASE statement is used to create a database in MySQL.

Syntax

CREATE DATABASE database_name

To learn more about SQL, please visit our SQL tutorial.To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example creates a database called “my_db”:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

if (mysql_query(“CREATE DATABASE my_db”,$con))
   {
   echo “Database created”;
   }
else
   {
   echo “Error creating database: ” . mysql_error();
   }

mysql_close($con);
?>


Create a Table

The CREATE TABLE statement is used to create a table in MySQL.

Syntax

CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
column_name3 data_type,
….

)

To learn more about SQL, please visit our SQL tutorial.

We must add the CREATE TABLE statement to the mysql_query() function to execute the command.

Example

The following example creates a table named “Persons”, with three columns. The column names will be “FirstName”, “LastName” and “Age”:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

// Create database
if (mysql_query(“CREATE DATABASE my_db”,$con))
   {
   echo “Database created”;
   }
else
   {
   echo “Error creating database: ” . mysql_error();
   }

// Create table
mysql_select_db(“my_db”, $con);
$sql = “CREATE TABLE Persons
(
FirstName varchar(15),
LastName varchar(15),
Age int
)”;

// Execute query
mysql_query($sql,$con);

mysql_close($con);
?>

Important: A database must be selected before a table can be created. The database is selected with the mysql_select_db() function.

Note: When you create a database field of type varchar, you must specify the maximum length of the field, e.g. varchar(15).

The data type specifies what type of data the column can hold. For a complete reference of all the data types available in MySQL, go to our complete Data Types reference.


Primary Keys and Auto Increment Fields

Each table should have a primary key field.

A primary key is used to uniquely identify the rows in a table. Each primary key value must be unique within the table. Furthermore, the primary key field cannot be null because the database engine requires a value to locate the record.

The following example sets the personID field as the primary key field. The primary key field is often an ID number, and is often used with the AUTO_INCREMENT setting. AUTO_INCREMENT automatically increases the value of the field by 1 each time a new record is added. To ensure that the primary key field cannot be null, we must add the NOT NULL setting to the field.

Example

$sql = “CREATE TABLE Persons 
(
personID int NOT NULL AUTO_INCREMENT,
PRIMARY KEY(personID),
FirstName varchar(15),
LastName varchar(15),
Age int
)”;

mysql_query($sql,$con);


PHP MySQL Insert Into



The INSERT INTO statement is used to insert new records in a table.


Insert Data Into a Database Table

The INSERT INTO statement is used to add new records to a database table.

Syntax

It is possible to write the INSERT INTO statement in two forms.

The first form doesn’t specify the column names where the data will be inserted, only their values:

INSERT INTO table_name VALUES (value1, value2, value3,…)

The second form specifies both the column names and the values to be inserted:

INSERT INTO table_name (column1, column2, column3,…) VALUES (value1, value2, value3,…)

To learn more about SQL, please visit our SQL tutorial.To get PHP to execute the statements above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

In the previous chapter we created a table named “Persons”, with three columns; “Firstname”, “Lastname” and “Age”. We will use the same table in this example. The following example adds two new records to the “Persons” table:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

mysql_query(“INSERT INTO Persons (FirstName, LastName, Age)
VALUES (‘Peter’, ‘Griffin’, ’35′)”);

mysql_query(“INSERT INTO Persons (FirstName, LastName, Age)
VALUES (‘Glenn’, ‘Quagmire’, ’33′)”);

mysql_close($con);
?>


Insert Data From a Form Into a Database

Now we will create an HTML form that can be used to add new records to the “Persons” table.

Here is the HTML form:

<html>
<body>

<form action=”insert.php” method=”post”>
Firstname: <input type=”text” name=”firstname” />
Lastname: <input type=”text” name=”lastname” />
Age: <input type=”text” name=”age” />
<input type=”submit” />
</form>

</body>
</html>

When a user clicks the submit button in the HTML form in the example above, the form data is sent to “insert.php”.

The “insert.php” file connects to a database, and retrieves the values from the form with the PHP $_POST variables.

Then, the mysql_query() function executes the INSERT INTO statement, and a new record will be added to the “Persons” table.

Here is the “insert.php” page:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

$sql=”INSERT INTO Persons (FirstName, LastName, Age)
VALUES
(‘$_POST[firstname]‘,’$_POST[lastname]‘,’$_POST[age]‘)”;

if (!mysql_query($sql,$con))
   {
   die(‘Error: ‘ . mysql_error());
   }
echo “1 record added”;

mysql_close($con)
?>


PHP MySQL Select



The SELECT statement is used to select data from a database.


Select Data From a Database Table

The SELECT statement is used to select data from a database.

Syntax

SELECT column_name(s) FROM table_name

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example selects all the data stored in the “Persons” table (The * character selects all the data in the table):

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

$result = mysql_query(“SELECT * FROM Persons”);

while($row = mysql_fetch_array($result))
   {
   echo $row['FirstName'] . ” ” . $row['LastName'];
   echo “<br />”;
   }

mysql_close($con);
?>

The example above stores the data returned by the mysql_query() function in the $result variable.

Next, we use the mysql_fetch_array() function to return the first row from the recordset as an array. Each call to mysql_fetch_array() returns the next row in the recordset. The while loop loops through all the records in the recordset. To print the value of each row, we use the PHP $row variable ($row['FirstName'] and $row['LastName']).

The output of the code above will be:

Peter Griffin
Glenn Quagmire

Display the Result in an HTML Table

The following example selects the same data as the example above, but will display the data in an HTML table:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

$result = mysql_query(“SELECT * FROM Persons”);

echo <table border=’1′>
<
tr>
<th>Firstname</th>
<th>Lastname</th>
</tr>”;

while($row = mysql_fetch_array($result))
   {
   echo “<tr>”;
   echo “<td>” . $row['FirstName'] . “</td>”;
   echo “<td>” . $row['LastName'] . “</td>”;
   echo “</tr>”;
   }
echo “</table>”;

mysql_close($con);
?>

The output of the code above will be:

Firstname Lastname
Glenn Quagmire
Peter Griffin

PHP MySQL The Where Clause



The WHERE clause is used to filter records.


The WHERE clause

The WHERE clause is used to extract only those records that fulfill a specified criterion.

Syntax

SELECT column_name(s) FROM table_name WHERE column_name operator value

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example selects all rows from the “Persons” table where “FirstName=’Peter’:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

$result = mysql_query(“SELECT * FROM Persons
WHERE FirstName=’Peter’”);

while($row = mysql_fetch_array($result))
   {
   echo $row['FirstName'] . ” ” . $row['LastName'];
   echo “<br />”;
   }
?>

The output of the code above will be:

Peter Griffin

PHP MySQL Order By Keyword



The ORDER BY keyword is used to sort the data in a recordset.


The ORDER BY Keyword

The ORDER BY keyword is used to sort the data in a recordset.

The ORDER BY keyword sort the records in ascending order by default.

If you want to sort the records in a descending order, you can use the DESC keyword.

Syntax

SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC

To learn more about SQL, please visit our SQL tutorial.

Example

The following example selects all the data stored in the “Persons” table, and sorts the result by the “Age” column:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

$result = mysql_query(“SELECT * FROM Persons ORDER BY age”);

while($row = mysql_fetch_array($result))
   {
   echo $row['FirstName'];
   echo ” ” . $row['LastName'];
   echo ” ” . $row['Age'];
   echo “<br />”;
   }

mysql_close($con);
?>

The output of the code above will be:

Glenn Quagmire 33
Peter Griffin 35

Order by Two Columns

It is also possible to order by more than one column. When ordering by more than one column, the second column is only used if the values in the first column are equal:

SELECT column_name(s) FROM table_name ORDER BY column1, column2

PHP MySQL Update



The UPDATE statement is used to modify data in a table.


Update Data In a Database

The UPDATE statement is used to update existing records in a table.

Syntax

UPDATE table_name SET column1=value, column2=value2,… WHERE some_column=some_value

Note: Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

Earlier in the tutorial we created a table named “Persons”. Here is how it looks:

FirstName LastName Age
Peter Griffin 35
Glenn Quagmire 33

The following example updates some data in the “Persons” table:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

mysql_query(“UPDATE Persons SET Age = ’36′
WHERE FirstName = ‘Peter’ AND LastName = ‘Griffin’”);

mysql_close($con);
?>

After the update, the “Persons” table will look like this:

FirstName LastName Age
Peter Griffin 36
Glenn Quagmire 33

PHP MySQL Delete



The DELETE statement is used to delete records in a table.


Delete Data In a Database

The DELETE FROM statement is used to delete records from a database table.

Syntax

DELETE FROM table_name
WHERE some_column = some_value

Note: Notice the WHERE clause in the DELETE syntax. The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

Look at the following “Persons” table:

FirstName LastName Age
Peter Griffin 35
Glenn Quagmire 33

The following example deletes all the records in the “Persons” table where LastName=’Griffin’:

<?php
$con = mysql_connect(“localhost”,”peter”,”abc123″);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“my_db”, $con);

mysql_query(“DELETE FROM Persons WHERE LastName=’Griffin’”);

mysql_close($con);
?>

After the deletion, the table will look like this:

FirstName LastName Age
Glenn Quagmire 33

PHP Database ODBC



ODBC is an Application Programming Interface (API) that allows you to connect to a data source (e.g. an MS Access database).


Create an ODBC Connection

With an ODBC connection, you can connect to any database, on any computer in your network, as long as an ODBC connection is available.

Here is how to create an ODBC connection to a MS Access Database: 

  1. Open the Administrative Tools icon in your Control Panel.
  2. Double-click on the Data Sources (ODBC) icon inside.
  3. Choose the System DSN tab.
  4. Click on Add in the System DSN tab.
  5. Select the Microsoft Access Driver. Click Finish.
  6. In the next screen, click Select to locate the database.
  7. Give the database a Data Source Name (DSN).
  8. Click OK.

Note that this configuration has to be done on the computer where your web site is located. If you are running Internet Information Server (IIS) on your own computer, the instructions above will work, but if your web site is located on a remote server, you have to have physical access to that server, or ask your web host to to set up a DSN for you to use.


Connecting to an ODBC

The odbc_connect() function is used to connect to an ODBC data source. The function takes four parameters: the data source name, username, password, and an optional cursor type.

The odbc_exec() function is used to execute an SQL statement.

Example

The following example creates a connection to a DSN called northwind, with no username and no password. It then creates an SQL and executes it:

$conn=odbc_connect(‘northwind’,”,”);
$sql=”SELECT * FROM customers”;
$rs=odbc_exec($conn,$sql);

Retrieving Records

The odbc_fetch_row() function is used to return records from the result-set. This function returns true if it is able to return rows, otherwise false.

The function takes two parameters: the ODBC result identifier and an optional row number:

odbc_fetch_row($rs)

Retrieving Fields from a Record

The odbc_result() function is used to read fields from a record. This function takes two parameters: the ODBC result identifier and a field number or name.

The code line below returns the value of the first field from the record:

$compname=odbc_result($rs,1);

The code line below returns the value of a field called “CompanyName”:

$compname=odbc_result($rs,”CompanyName”);

Closing an ODBC Connection

The odbc_close() function is used to close an ODBC connection.

odbc_close($conn);

An ODBC Example

The following example shows how to first create a database connection, then a result-set, and then display the data in an HTML table.

<html>
<body>

<?php
$conn=odbc_connect(‘northwind’,”,”);
if (!$conn)
   {exit(“Connection Failed: ” . $conn);}
$sql=”SELECT * FROM customers”;
$rs=odbc_exec($conn,$sql);
if (!$rs)
   {exit(“Error in SQL”);}
echo “<table><tr>”;
echo “<th>Companyname</th>”;
echo “<th>Contactname</th></tr>”;
while (odbc_fetch_row($rs))
   {
   $compname=odbc_result($rs,”CompanyName”);
   $conname=odbc_result($rs,”ContactName”);
   echo “<tr><td>$compname</td>”;
   echo “<td>$conname</td></tr>”;
   }
odbc_close($conn);
echo “</table>”;
?>

</body>
</html>


PHP XML Expat Parser



The built-in Expat parser makes it possible to process XML documents in PHP.


What is XML?

XML is used to describe data and to focus on what data is. An XML file describes the structure of the data.

In XML, no tags are predefined. You must define your own tags.

If you want to learn more about XML, please visit our XML tutorial.


What is Expat?

To read and update – create and manipulate – an XML document, you will need an XML parser.

There are two basic types of XML parsers:

  • Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the whole document, and provides access to the tree elements. e.g. the Document Object Model (DOM)
  • Event-based parser: Views an XML document as a series of events. When a specific event occurs, it calls a function to handle it

The Expat parser is an event-based parser.

Event-based parsers focus on the content of the XML documents, not their structure. Because of this, event-based parsers can access data faster than tree-based parsers.

Look at the following XML fraction:

<from>Jani</from>

An event-based parser reports the XML above as a series of three events:

  • Start element: from
  • Start CDATA section, value: Jani
  • Close element: from

The XML example above contains well-formed XML. However, the example is not valid XML, because there is no Document Type Definition (DTD) associated with it.

However, this makes no difference when using the Expat parser. Expat is a non-validating parser, and ignores any DTDs.

As an event-based, non-validating XML parser, Expat is fast and small, and a perfect match for PHP web applications.

Note: XML documents must be well-formed or Expat will generate an error.


Installation

The XML Expat parser functions are part of the PHP core. There is no installation needed to use these functions.


An XML File

The XML file below will be used in our example:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don’t forget me this weekend!</body>
</note>

Initializing the XML Parser

We want to initialize the XML parser in PHP, define some handlers for different XML events, and then parse the XML file.

Example

<?php
//Initialize the XML parser
$parser=xml_parser_create();

//Function to use at the start of an element
function start($parser,$element_name,$element_attrs)
   {
   switch($element_name)
     {
     case “NOTE”:
     echo “– Note –<br />”;
     break;
     case “TO”:
     echo “To: “;
     break;
     case “FROM”:
     echo “From: “;
     break;
     case “HEADING”:
     echo “Heading: “;
     break;
     case “BODY”:
     echo “Message: “;
     }
   }

//Function to use at the end of an element
function stop($parser,$element_name)
   {
   echo “<br />”;
   }

//Function to use when finding character data
function char($parser,$data)
   {
   echo $data;
   }

//Specify element handler
xml_set_element_handler($parser,”start”,”stop”);

//Specify data handler
xml_set_character_data_handler($parser,”char”);

//Open XML file
$fp=fopen(“test.xml”,”r”);

//Read data
while ($data=fread($fp,4096))
   {
   xml_parse($parser,$data,feof($fp)) or
   die (sprintf(“XML Error: %s at line %d”,
   xml_error_string(xml_get_error_code($parser)),
   xml_get_current_line_number($parser)));
   }

//Free the XML parser
xml_parser_free($parser);
?>

The output of the code above will be:

– Note –
To: Tove
From: Jani
Heading: Reminder
Message: Don’t forget me this weekend!

How it works:

  1. Initialize the XML parser with the xml_parser_create() function
  2. Create functions to use with the different event handlers
  3. Add the xml_set_element_handler() function to specify which function will be executed when the parser encounters the opening and closing tags
  4. Add the xml_set_character_data_handler() function to specify which function will execute when the parser encounters character data
  5. Parse the file “test.xml” with the xml_parse() function
  6. In case of an error, add  xml_error_string() function to convert an XML error to a textual description
  7. Call the xml_parser_free() function to release the memory allocated with the xml_parser_create() function

More PHP Expat Parser

For more information about the PHP Expat functions, visit our PHP XML Parser Reference.


PHP XML DOM



The built-in DOM parser makes it possible to process XML documents in PHP.


What is DOM?

The W3C DOM provides a standard set of objects for HTML and XML documents, and a standard interface for accessing and manipulating them.

The W3C DOM is separated into different parts (Core, XML, and HTML) and different levels (DOM Level 1/2/3):

* Core DOM – defines a standard set of objects for any structured document
* XML DOM – defines a standard set of objects for XML documents
* HTML DOM – defines a standard set of objects for HTML documents

If you want to learn more about the XML DOM, please visit our XML DOM tutorial.


XML Parsing

To read and update – create and manipulate – an XML document, you will need an XML parser.

There are two basic types of XML parsers:

  • Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the whole document, and provides access to the tree elements
  • Event-based parser: Views an XML document as a series of events. When a specific event occurs, it calls a function to handle it

The DOM parser is an tree-based parser.

Look at the following XML document fraction:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<from>Jani</from>

The XML DOM sees the XML above as a tree structure:

  • Level 1: XML Document
  • Level 2: Root element: <from>
  • Level 3: Text element: “Jani”

Installation

The DOM XML parser functions are part of the PHP core. There is no installation needed to use these functions.


An XML File

The XML file below will be used in our example:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don’t forget me this weekend!</body>
</note>

Load and Output XML

We want to initialize the XML parser, load the xml, and output it:

Example

<?php
$xmlDoc = new DOMDocument();
$xmlDoc->load(“note.xml”);

print $xmlDoc->saveXML();
?>

The output of the code above will be:

Tove Jani Reminder Don’t forget me this weekend!

If you select “View source” in the browser window, you will see the following HTML:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don’t forget me this weekend!</body>
</note>

The example above creates a DOMDocument-Object and loads the XML from “note.xml” into it.

Then the saveXML() function to puts the internal XML document into a string, so we can output it.


Looping through XML

We want to initialize the XML parser, load the XML, and loop through all elements of the <note> element:

Example

<?php
$xmlDoc = new DOMDocument();
$xmlDoc->load(“note.xml”);

$x = $xmlDoc->documentElement;
foreach ($x->childNodes AS $item)
   {
   print $item->nodeName . ” = ” . $item->nodeValue . “<br />”;
   }
?>

The output of the code above will be:

#text =
to = Tove
#text =
from = Jani
#text =
heading = Reminder
#text =
body = Don’t forget me this weekend!
#text =

In the example above you see that there are empty text nodes between each element.

When XML generates, it often contains white-spaces between the nodes. The XML DOM parser treats these as ordinary elements, and if you are not aware of them, they sometimes cause problems.


If you want to learn more about the XML DOM, please visit our XML DOM tutorial.


PHP SimpleXML



SimpleXML handles the most common XML tasks and leaves the rest for other extensions.


What is SimpleXML?

SimpleXML is new in PHP 5. It is an easy way of getting an element’s attributes and text, if you know the XML document’s layout.

Compared to DOM or the Expat parser, SimpleXML just takes a few lines of code to read text data from an element.

SimpleXML converts the XML document into an object, like this:

  • Elements – Are converted to single attributes of the SimpleXMLElement object. When there’s more than one element on one level, they’re placed inside an array
  • Attributes – Are accessed using associative arrays, where an index corresponds to the attribute name
  • Element Data – Text data from elements are converted to strings. If an element has more than one text node, they will be arranged in the order they are found

SimpleXML is fast and easy to use when performing basic tasks like:

  • Reading XML files
  • Extracting data from XML strings
  • Editing text nodes or attributes

However, when dealing with advanced XML, like namespaces, you are better off using the Expat parser or the XML DOM.


Installation

As of PHP 5.0, the SimpleXML functions are part of the PHP core. There is no installation needed to use these functions.


Using SimpleXML

Below is an XML file:

<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don’t forget me this weekend!</body>
</note>

We want to output the element names and data from the XML file above.

Here’s what to do:

  1. Load the XML file
  2. Get the name of the first element
  3. Create a loop that will trigger on each child node, using the children() function
  4. Output the element name and data for each child node

Example

<?php
$xml = simplexml_load_file(“test.xml”);

echo $xml->getName() . “<br />”;

foreach($xml->children() as $child)
   {
   echo $child->getName() . “: ” . $child . “<br />”;
   }
?>

The output of the code above will be:

note
to: Tove
from: Jani
heading: Reminder
body: Don’t forget me this weekend!

More PHP SimpleXML

For more information about the PHP SimpleXML functions, visit our PHP SimpleXML Reference.


AJAX Introduction



AJAX = Asynchronous JavaScript and XML

AJAX is not a new programming language, but a new technique for creating better, faster, and more interactive web applications.

With AJAX, a JavaScript can communicate directly with the server, with the XMLHttpRequest object. With this object, a JavaScript can trade data with a web server, without reloading the page.

AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages.

The AJAX technique makes Internet applications smaller, faster and more user-friendly.


AJAX is based on Internet standards

AJAX is based on the following web standards:

  • JavaScript
  • XML
  • HTML
  • CSS

AJAX applications are browser- and platform-independent.


AJAX is about better Internet-applications

Internet-applications have many benefits over desktop applications; they can reach a larger audience, they are easier to install and support, and easier to develop.

However, Internet-applications are not always as “rich” and user-friendly as traditional desktop applications.

With AJAX, Internet applications can be made richer and more user-friendly.


Start using AJAX today

There is nothing new to learn.

AJAX is based on existing standards. These standards have been used by developers for several years.


PHP and AJAX

There is no such thing as an AJAX server. AJAX runs in your browser. AJAX uses HTTP requests to request small pieces of information from the server, instead of whole pages.

In our PHP tutorial we will demonstrate how a web page can communicate with a PHP web server online.


AJAX XMLHttpRequest



The keystone of AJAX is the XMLHttpRequest object.


AJAX uses the XMLHttpRequest object

To get or send information from/to a database or a file on the server with traditional JavaScript, you will have to make an HTML form, and a user will have to click the “Submit” button to send/get the information, wait for the server to respond, then a new page will load with the results. Because the server returns a new page each time the user submits input, traditional web applications can run slowly and tend to be less user-friendly.

With AJAX, your JavaScript communicates directly with the server, through the JavaScript XMLHttpRequest object.

With the XMLHttpRequest object, a web page can make a request to, and get a response from a web server – without reloading the page. The user will stay on the same page, and he or she will not notice that scripts request pages, or send data to a server in the background.

The XMLHttpRequest object is supported in all major browsers (Internet Explorer, Firefox, Chrome, Opera, and Safari).


AJAX – Browser support

All new browsers use the built-in JavaScript XMLHttpRequest object to create an XMLHttpRequest object (IE5 and IE6 uses an ActiveXObject).

The JavaScript code for creating an XMLHttpRequest object:

if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }

The next chapter shows how to use the XMLHttpRequest object to communicate with a PHP server.


More about the XMLHttpRequest object

If you want to read more about the XMLHttpRequest, visit our AJAX tutorial.


PHP Example – AJAX Suggest



AJAX can be used to create more interactive applications.


AJAX Suggest example

The following AJAX example will demonstrate how a web page can communicate with a web server while a user enters data into an HTML form.

Type a name in the input field below:

First name: Suggestions:


Example explained – The HTML page

The HTML page contains a link to an external JavaScript, a simple HTML form, and a span element:

<html>
<head>
<script type=”text/javascript” src=”clienthint.js”></script>
</head>
<body>

<form>
First Name: <input type=”text” id=”txt1″ onkeyup=”showHint(this.value)” />
</form>
<p>Suggestions: <span id=”txtHint”></span></p>

</body>
</html>

The HTML form above has an input field called “txt1″. An event attribute for this field defines a function to be triggered by the onkeyup event.

The paragraph below the form contains a span called “txtHint”. The span is used as a placeholder for data retrieved from the web server.

When a user inputs data, the function called “showHint()” is executed. The execution of the function is triggered by the “onkeyup” event. In other words: Each time a user moves the finger away from a keyboard key inside the input field, the function showHint is called.


Example explained – The JavaScript code

This is the JavaScript code, stored in the file “clienthint.js”:

var xmlhttp

function showHint(str)
{
if (str.length==0)
  {
  document.getElementById(“txtHint”).innerHTML=””;
  return;
  }
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
  {
  alert (“Your browser does not support XMLHTTP!”);
  return;
  }
var url=”gethint.php”;
url=url+”?q=”+str;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
  {
  document.getElementById(“txtHint”).innerHTML=xmlhttp.responseText;
  }
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The showHint() function

The showHint() function above is executed every time a character is entered in the “txt1″ input field.

If there is input in the input field (str.length > 0), the showHint() function executes the following:

  • Calls the GetXmlHttpObject() function to create an XMLHTTP object
  • Defines the URL (filename) to send to the server
  • Adds a parameter (q) to the URL with the content of the input field
  • Adds a random number to prevent the server from using a cached file
  • Each time the readyState property changes, the stateChanged() function will be executed
  • Opens the XMLHTTP object with the given URL
  • Sends an HTTP request to the server

If the input field is empty, the function simply clears the content of the txtHint placeholder.

The GetXmlHttpObject() function

The showHint() function above calls a function named GetXmlHttpObject().

The purpose of the GetXmlHttpObject() function is to solve the problem of creating different XMLHTTP objects for different browsers.

The stateChanged() function

The stateChanged() function executes every time the state of the XMLHTTP object changes.

When the state changes to 4 (“complete”), the content of the txtHint placeholder is filled with the response text.


Example explained – The PHP page

The code in the “gethint.php” checks an array of names and returns the corresponding names to the client:

<?php
// Fill up array with names
$a[]=”Anna”;
$a[]=”Brittany”;
$a[]=”Cinderella”;
$a[]=”Diana”;
$a[]=”Eva”;
$a[]=”Fiona”;
$a[]=”Gunda”;
$a[]=”Hege”;
$a[]=”Inga”;
$a[]=”Johanna”;
$a[]=”Kitty”;
$a[]=”Linda”;
$a[]=”Nina”;
$a[]=”Ophelia”;
$a[]=”Petunia”;
$a[]=”Amanda”;
$a[]=”Raquel”;
$a[]=”Cindy”;
$a[]=”Doris”;
$a[]=”Eve”;
$a[]=”Evita”;
$a[]=”Sunniva”;
$a[]=”Tove”;
$a[]=”Unni”;
$a[]=”Violet”;
$a[]=”Liza”;
$a[]=”Elizabeth”;
$a[]=”Ellen”;
$a[]=”Wenche”;
$a[]=”Vicky”;

//get the q parameter from URL
$q=$_GET["q"];

//lookup all hints from array if length of q>0
if (strlen($q) > 0)
  {
  $hint=””;
  for($i=0; $i<count($a); $i++)
    {
    if (strtolower($q)==strtolower(substr($a[$i],0,strlen($q))))
      {
      if ($hint==””)
        {
        $hint=$a[$i];
        }
      else
        {
        $hint=$hint.” , “.$a[$i];
        }
      }
    }
  }

// Set output to “no suggestion” if no hint were found
// or to the correct values
if ($hint == “”)
  {
  $response=”no suggestion”;
  }
else
  {
  $response=$hint;
  }

//output the response
echo $response;
?>

If there is any text sent from the JavaScript (strlen($q) > 0), the following happens:

  1. Find a name matching the characters sent from the JavaScript
  2. If no match were found, set the response string to “no suggestion”
  3. If one or more matching names were found, set the response string to all these names
  4. The response is sent to the “txtHint” placeholder

PHP Example – AJAX and XML



AJAX can be used for interactive communication with an XML file.


AJAX XML example

The following example will demonstrate how a web page can fetch information from an XML file with AJAX technology.

Select a CD: Bob Dylan Bee Gees Cat Stevens

CD info will be listed here…

Example explained – The HTML page

The HTML page contains a link to an external JavaScript, an HTML form, and a div element:

<html>
<head>
<script type=”text/javascript” src=”selectcd.js”></script>
</head>

<body>

<form>
Select a CD:
<select name=”cds” onchange=”showCD(this.value)”>
<option value=”Bob Dylan”>Bob Dylan</option>
<option value=”Bonnie Tyler”>Bonnie Tyler</option>
<option value=”Dolly Parton”>Dolly Parton</option>
</select>
</form>

<div id=”txtHint”><b>CD info will be listed here…</b></div>

</body>
</html>

As you can see it is just a simple HTML form  with a simple drop down box called “cds”.

The <div> below the form will be used as a placeholder for info retrieved from the web server.

When the user selects data, a function called “showCD” is executed. The execution of the function is triggered by the “onchange” event. In other words: Each time the user change the value in the drop down box, the function showCD is called.


Example explained – The JavaScript code

This is the JavaScript code stored in the file “selectcd.js”:

var xmlhttp

function showCD(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
  {
  alert (“Your browser does not support AJAX!”);
  return;
  }
var url=”getcd.php”;
url=url+”?q=”+str;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById(“txtHint”).innerHTML=xmlhttp.responseText;
}
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The stateChanged() and GetXmlHttpObject functions are the same as in the PHP AJAX Suggest chapter, you can go to there for an explanation of those.

The showUser() Function

When a person in the drop-down box is selected, the showUser() function executes the following:

  1. Calls the GetXmlHttpObject() function to create an XMLHTTP object
  2. Defines an URL (filename) to send to the server
  3. Adds a parameter (q) to the URL with the content of the drop-down box
  4. Adds a random number to prevent the server from using a cached file
  5. Each time the readyState property changes, the stateChanged() function will be executed
  6. Opens the XMLHTTP object with the given URL
  7. Sends an HTTP request to the server

Example explained – The PHP Page

The server paged called by the JavaScript, is a PHP file called “getcd.php”.

The PHP script loads an XML document, “cd_catalog.xml”, runs a query against the XML file, and returns the result as HTML:

<?php
$q=$_GET["q"];

$xmlDoc = new DOMDocument();
$xmlDoc->load(“cd_catalog.xml”);

$x=$xmlDoc->getElementsByTagName(‘ARTIST’);

for ($i=0; $i<=$x->length-1; $i++)
{
//Process only element nodes
if ($x->item($i)->nodeType==1)
   {
   if ($x->item($i)->childNodes->item(0)->nodeValue == $q)
     {
     $y=($x->item($i)->parentNode);
     }
   }
}

$cd=($y->childNodes);

for ($i=0;$i<$cd->length;$i++)
{
//Process only element nodes
if ($cd->item($i)->nodeType==1)
   {
   echo($cd->item($i)->nodeName);
   echo(“: “);
   echo($cd->item($i)->childNodes->item(0)->nodeValue);
   echo(“<br />”);
   }
}
?>

When the CD query is sent from the JavaScript to the PHP page, the following happens:

  1. PHP creates an XML DOM object
  2. Find all <artist> elements that matches the name sent from the JavaScript
  3. Output the album information (send to the “txtHint” placeholder)

PHP Example – AJAX and MySQL



AJAX can be used for interactive communication with a database.


AJAX database example

The following example will demonstrate how a web page can fetch information from a database with AJAX technology.

Select a person: Peter Griffin Lois Griffin Joseph Swanson Glenn Quagmire

Person info will be listed here.

Example explained – The MySQL Database

The database table we use in this example looks like this:

id FirstName LastName Age Hometown Job
1 Peter Griffin 41 Quahog Brewery
2 Lois Griffin 40 Newport Piano Teacher
3 Joseph Swanson 39 Quahog Police Officer
4 Glenn Quagmire 41 Quahog Pilot

 


Example explained – The HTML page

The HTML page contains a link to an external JavaScript, an HTML form, and a div element:

<html>
<head>
<script type=”text/javascript” src=”selectuser.js”></script>
</head>
<body>

<form>
Select a User:
<select name=”users” onchange=”showUser(this.value)”>
<option value=”1″>Peter Griffin</option>
<option value=”2″>Lois Griffin</option>
<option value=”3″>Glenn Quagmire</option>
<option value=”4″>Joseph Swanson</option>
</select>
</form>
<br />
<div id=”txtHint”><b>Person info will be listed here.</b></div>

</body>
</html>

As you can see it is just a simple HTML form with a drop down box called “customers”.

The <div> below the form will be used as a placeholder for info retrieved from the web server.

When the user selects data, a function called “showUser()” is executed. The execution of the function is triggered by the “onchange” event. In other words: Each time the user change the value in the drop down box, the function showUser() is called.


Example explained – The JavaScript code

This is the JavaScript code stored in the file “selectuser.js”:

var xmlhttp;

function showUser(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
   {
   alert (“Browser does not support HTTP Request”);
   return;
   }
var url=”getuser.php”;
url=url+”?q=”+str;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById(“txtHint”).innerHTML=xmlhttp.responseText;
}
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The stateChanged() and GetXmlHttpObject functions are the same as in the PHP AJAX Suggest chapter, you can go to there for an explanation of those.

The showUser() Function

When a person in the drop-down box is selected, the showUser() function executes the following:

  1. Calls the GetXmlHttpObject() function to create an XMLHTTP object
  2. Defines an URL (filename) to send to the server
  3. Adds a parameter (q) to the URL with the content of the drop-down box
  4. Adds a random number to prevent the server from using a cached file
  5. Each time the readyState property changes, the stateChanged() function will be executed
  6. Opens the XMLHTTP object with the given URL
  7. Sends an HTTP request to the server

Example explained – The PHP Page

The PHP page called by the JavaScript, is called “getuser.php”.

The PHP script runs an SQL query against a MySQL database, and returns the result as HTML:

<?php
$q=$_GET["q"];

$con = mysql_connect(‘localhost’, ‘peter’, ‘abc123′);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“ajax_demo”, $con);

$sql=”SELECT * FROM user WHERE id = ‘”.$q.”‘”;

$result = mysql_query($sql);

echo “<table border=’1′>
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
<th>Hometown</th>
<th>Job</th>
</tr>”;

while($row = mysql_fetch_array($result))
   {
   echo “<tr>”;
   echo “<td>” . $row['FirstName'] . “</td>”;
   echo “<td>” . $row['LastName'] . “</td>”;
   echo “<td>” . $row['Age'] . “</td>”;
   echo “<td>” . $row['Hometown'] . “</td>”;
   echo “<td>” . $row['Job'] . “</td>”;
   echo “</tr>”;
   }
echo “</table>”;

mysql_close($con);
?>

When the query is sent from the JavaScript to the PHP page, the following happens:

  1. PHP opens a connection to a MySQL server
  2. The correct person is found
  3. An HTML table is created, and filled with data, and sent back to the “txtHint” placeholder

PHP Example – responseXML



responseText returns the HTTP response as a string.

responseXML returns the response as XML.


AJAX ResponseXML example

The ResponseXML property returns an XML document object, which can be examined and parsed using the DOM.

The following example will demonstrate how a web page can fetch information from a database with AJAX technology. The selected data from the database will this time be converted to an XML document, and then we will use the DOM to extract the values to be displayed.

This example might look equal to the “PHP AJAX and MySQL” example in the previous chapter. However, there is a big difference: this time we get the data from the PHP page as XML, with the responseXML function.

Receiving the response as an XML document allows us to update this page several places, instead of just receiving an HTML output, and displaying it.

In this example we will update several <span> elements with the information we receive from the database.

Select a User: Peter Griffin Lois Griffin Joseph Swanson Glenn Quagmire

Example explained – The MySQL Database

The database table we use in this example looks like this:

id FirstName LastName Age Hometown Job
1 Peter Griffin 41 Quahog Brewery
2 Lois Griffin 40 Newport Piano Teacher
3 Joseph Swanson 39 Quahog Police Officer
4 Glenn Quagmire 41 Quahog Pilot

 


Example explained – The HTML page

The HTML page contains a link to an external JavaScript, an HTML form, and several <span> elements:

<html>
<head>
<script type=”text/javascript” src=”responsexml.js”></script>
</head>
<body>

<form>
Select a User:
<select name=”users” onchange=”showUser(this.value)”>
<option value=”1″>Peter Griffin</option>
<option value=”2″>Lois Griffin</option>
<option value=”3″>Glenn Quagmire</option>
<option value=”4″>Joseph Swanson</option>
</select>
</form>

<h2><span id=”firstname”></span>&nbsp;<span id=”lastname”></span></h2>
<span id=”job”></span>
<div style=”text-align: right”>
  <span id=”age_text”></span>
  <span id=”age”></span>
  <span id=”hometown_text”></span>
  <span id=”hometown”></span>
</div>

</body>
</html>

  • The HTML form contains a drop-down box called “users”, with id and names from the database table, as options
  • The <span> elements are placeholders for the values we will receive
  • When a user is selected, a function called “showUser()” is executed (triggered by the “onchange” event)

In other words: Each time a user changes the value in the drop-down box, the function showUser() is called, and outputs the result in the <span> elements.


Example explained – The JavaScript code

This is the JavaScript code stored in the file “responsexml.js”:

var xmlhttp;

function showUser(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
   {
   alert (“Browser does not support HTTP Request”);
   return;
   }
var url=”responsexml.php”;
url=url+”?q=”+str;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
   {
   xmlDoc=xmlhttp.responseXML;
   document.getElementById(“firstname”).innerHTML=
   xmlDoc.getElementsByTagName(“firstname”)[0].childNodes[0].nodeValue;
   document.getElementById(“lastname”).innerHTML=
   xmlDoc.getElementsByTagName(“lastname”)[0].childNodes[0].nodeValue;
   document.getElementById(“job”).innerHTML=
   xmlDoc.getElementsByTagName(“job”)[0].childNodes[0].nodeValue;
   document.getElementById(“age_text”).innerHTML=”Age: “;
   document.getElementById(“age”).innerHTML=
   xmlDoc.getElementsByTagName(“age”)[0].childNodes[0].nodeValue;
   document.getElementById(“hometown_text”).innerHTML=”<br/>From: “;
   document.getElementById(“hometown”).innerHTML=
   xmlDoc.getElementsByTagName(“hometown”)[0].childNodes[0].nodeValue;
   }
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The showUser() and GetXmlHttpObject functions are the same as in the PHP AJAX and MySQL chapter, you can go to there for an explanation of those.

The stateChanged() Function

When an option in the drop-down box is selected, the function executes the following:

  1. Sets xmlDoc variable as an XML document, using the responseXML function
  2. Retrieves data from the XML document, and place it in the correct <span> element

Example explained – The PHP Page

The PHP page called by the JavaScript, is called “responsexml.php”.

The PHP script runs an SQL query against a MySQL database, and returns the result an XML document:

<?php
$q=$_GET["q"];

$con = mysql_connect(‘localhost’, ‘peter’, ‘abc123′);
if (!$con)
   {
   die(‘Could not connect: ‘ . mysql_error());
   }

mysql_select_db(“ajax_demo”, $con);

$sql=”SELECT * FROM user WHERE id = “.$q.””;

$result = mysql_query($sql);

echo ‘<?xml version=”1.0″ encoding=”ISO-8859-1″?>
<person>’;
while($row = mysql_fetch_array($result))
   {
   echo “<firstname>” . $row['FirstName'] . “</firstname>”;
   echo “<lastname>” . $row['LastName'] . “</lastname>”;
   echo “<age>” . $row['Age'] . “</age>”;
   echo “<hometown>” . $row['Hometown'] . “</hometown>”;
   echo “<job>” . $row['Job'] . “</job>”;
   }
echo “</person>”;

mysql_close($con);
?>

When the query is sent from the JavaScript to the PHP page, the following happens:

  1. Set the $q variable to the data sent in the q parameter
  2. Open a connection to a MySQL server
  3. The “user” with the specified id is found
  4. The data is outputted as an XML document

PHP Example – AJAX Live Search



AJAX can be used for a more user-friendly and interactive search.


AJAX Live Search

In this example we will demonstrate a live search, where you get search results while you type.

Live search has many benefits compared to traditional searching:

  • Results are shown as you type
  • Results narrow as you continue typing
  • If results become too narrow, remove characters to see a broader result

Search for a W3Schools page in the input field below:

In the example above, the results are found in an XML document (links.xml). To make this example small and simple, only eight results are available.


Example Explained – The HTML page

The HTML page contains a link to an external JavaScript, some style definitions, an HTML form, and a div element:

<html>
<head>
<script type=”text/javascript” src=”livesearch.js”></script>
<style type=”text/css”>
#livesearch
   {
   margin:0px;
   width:194px;
   }
#txt1
   {
   margin:0px;
   }
</style>
</head>
<body>

<form>
<input type=”text” id=”txt1″ size=”30″ onkeyup=”showResult(this.value)” />
<div id=”livesearch”></div>
</form>

</body>
</html>

The HTML form works like this:

  1. An event is triggered when the user presses, and releases a key in the input field
  2. When the event is triggered, the function showResult() is executed
  3. The <div id=”livesearch”> is a placeholder for the data returned from the showResult() function

Example Explained – The JavaScript code

This is the JavaScript code stored in the file “livesearch.js”:

var xmlhttp;

function showResult(str)
{
if (str.length==0)
   {
   document.getElementById(“livesearch”).innerHTML=””;
   document.getElementById(“livesearch”).style.border=”0px”;
   return;
   }
xmlhttp=GetXmlHttpObject()
if (xmlhttp==null)
   {
   alert (“Your browser does not support XML HTTP Request”);
   return;
   }
var url=”livesearch.php”;
url=url+”?q=”+str;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged ;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
   {
   document.getElementById(“livesearch”).innerHTML=xmlhttp.responseText;
   document.getElementById(“livesearch”).style.border=”1px solid #A5ACB2″;
   }
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The GetXmlHttpObject() function is the same as in the PHP AJAX Suggest chapter.

The showResult() Function

This function executes every time a character is entered in the input field. If there is no input in the text field (str.length == 0), the function sets the return field to empty and removes the border around it. However, if there is any input in the text field, the function executes the following:

  1. Calls the GetXmlHttpObject() function to create an XMLHTTP object
  2. Defines the URL (filename) to send to the server
  3. Adds a parameter (q) to the URL with the content of the input field
  4. Adds a random number to prevent the server from using a cached file
  5. Each time the readyState property changes, the stateChanged() function will be executed
  6. Opens the XMLHTTP object with the given URL
  7. Sends an HTTP request to the server

The stateChanged() Function

This function executes every time the state of the XMLHTTP object changes. When the state changes to 4 (“complete”), the content of the txtHint placeholder is filled with the response text, and a border is set around the field.


Example Explained – The PHP page

The PHP page called by the JavaScript code is called “livesearch.php”.

The code searches an XML file for titles matching the search string and returns the result as HTML:

<?php
$xmlDoc = new DOMDocument();
$xmlDoc->load(“links.xml”);

$x=$xmlDoc->getElementsByTagName(‘link’);

//get the q parameter from URL
$q=$_GET["q"];

//lookup all links from the xml file if length of q>0
if (strlen($q) > 0)
{
$hint=””;
for($i=0; $i<($x->length); $i++)
   {
   $y=$x->item($i)->getElementsByTagName(‘title’);
   $z=$x->item($i)->getElementsByTagName(‘url’);
   if ($y->item(0)->nodeType==1)
     {
     //find a link matching the search text
     if (stristr($y->item(0)->childNodes->item(0)->nodeValue,$q))
       {
       if ($hint==””)
         {
         $hint=”<a href=’” .
         $z->item(0)->childNodes->item(0)->nodeValue .
         “‘ target=’_blank’>” .
         $y->item(0)->childNodes->item(0)->nodeValue . “</a>”;
         }
       else
         {
         $hint=$hint . “<br /><a href=’” .
         $z->item(0)->childNodes->item(0)->nodeValue .
         “‘ target=’_blank’>” .
         $y->item(0)->childNodes->item(0)->nodeValue . “</a>”;
         }
       }
     }
   }
}

// Set output to “no suggestion” if no hint were found
// or to the correct values
if ($hint == “”)
   {
   $response=”no suggestion”;
   }
else
   {
   $response=$hint;
   }

//output the response
echo $response;
?>

If there is any text sent from the JavaScript (strlen($q) > 0), the following happens:

  1. PHP creates an XML DOM object of the “links.xml” file
  2. Loops through all  <title> elements to find titles that match the text sent from the JavaScript
  3. Sets the correct link and title in the “$response” variable. If more than one match is found, all matches are added to the variable
  4. If no matches are found, the $response variable is set to “no suggestion”
  5. Output the $respone variable to the “livesearch” placeholder

PHP Example – AJAX RSS Reader



An RSS Reader is used to read RSS Feeds.


AJAX RSS Reader

In this example we will demonstrate an RSS reader, where the content from the RSS is loaded into a webpage without refreshing.

Select an RSS-feed: Google News MSNBC News

RSS-feed will be listed here…

Example Explained – The HTML page

The HTML page contains a link to an external JavaScript, an HTML form, and a div element:

<html>
<head>
<script type=”text/javascript” src=”getrss.js”></script>
</head>
<body>

<form>
Select an RSS-feed:
<select onchange=”showRSS(this.value)”>
<option value=”Google”>Google News</option>
<option value=”MSNBC”>MSNBC News</option>
</select>
</form>

<p><div id=”rssOutput”>
<b>RSS-feed will be listed here…</b></div></p>
</body>
</html>

The HTML form works like this:

  1. An event is triggered when a user selects an option in the drop-down box
  2. When the event is triggered, the function showRSS() is executed
  3. The <div id=”rssOutput”> is a placeholder for the data returned from the showRSS() function

Example Explained – The JavaScript code

This is the JavaScript code stored in the file “getrss.js”:

var xmlhttp;

function showRSS(str)
   {
   xmlhttp=GetXmlHttpObject();
   if (xmlhttp==null)
     {
     alert (“Your browser does not support XML HTTP Request”);
     return;
     }
   var url=”getrss.php”;
   url=url+”?q=”+str;
   url=url+”&sid=”+Math.random();
   xmlhttp.onreadystatechange=stateChanged;
   xmlhttp.open(“GET”,url,true);
   xmlhttp.send(null);
   }

function stateChanged()
   {
   if (xmlhttp.readyState==4)
     {
     document.getElementById(“rssOutput”).innerHTML=xmlhttp.responseText;
     }
   }

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();
  }
if (window.ActiveXObject)
  {
  // code for IE6, IE5
  return new ActiveXObject(“Microsoft.XMLHTTP”);
  }
return null;
}

The stateChanged() and GetXmlHttpObject functions are the same as in the PHP AJAX Suggest chapter.

The showRSS() Function

Every time an option is selected in the input field, this function executes the following:

  1. Calls the GetXmlHttpObject() function to create an XMLHTTP object
  2. Defines the URL (filename) to send to the server
  3. Adds a parameter (q) to the URL with the selected option from the drop-down list
  4. Adds a random number to prevent the server from using a cached file
  5. Each time the readyState property changes, the stateChanged() function will be executed
  6. Opens the XMLHTTP object with the given URL
  7. Sends an HTTP request to the server

Example Explained – The PHP page

The PHP page called by the JavaScript code is called “getrss.php”:

<?php
//get the q parameter from URL
$q=$_GET["q"];

//find out which feed was selected
if($q==”Google”)
   {
   $xml=(“http://news.google.com/news?ned=us&topic=h&output=rss&#8221;);
   }
elseif($q==”MSNBC”)
   {
   $xml=(“http://rss.msnbc.msn.com/id/3032091/device/rss/rss.xml&#8221;);
   }

$xmlDoc = new DOMDocument();
$xmlDoc->load($xml);

//get elements from “<channel>”
$channel=$xmlDoc->getElementsByTagName(‘channel’)->item(0);
$channel_title = $channel->getElementsByTagName(‘title’)
->item(0)->childNodes->item(0)->nodeValue;
$channel_link = $channel->getElementsByTagName(‘link’)
->item(0)->childNodes->item(0)->nodeValue;
$channel_desc = $channel->getElementsByTagName(‘description’)
->item(0)->childNodes->item(0)->nodeValue;

//output elements from “<channel>”
echo(“<p><a href=’” . $channel_link
   . “‘>” . $channel_title . “</a>”);
echo(“<br />”);
echo($channel_desc . “</p>”);

//get and output “<item>” elements
$x=$xmlDoc->getElementsByTagName(‘item’);
for ($i=0; $i<=2; $i++)
   {
   $item_title=$x->item($i)->getElementsByTagName(‘title’)
   ->item(0)->childNodes->item(0)->nodeValue;
   $item_link=$x->item($i)->getElementsByTagName(‘link’)
   ->item(0)->childNodes->item(0)->nodeValue;
   $item_desc=$x->item($i)->getElementsByTagName(‘description’)
   ->item(0)->childNodes->item(0)->nodeValue;

   echo (“<p><a href=’” . $item_link
   . “‘>” . $item_title . “</a>”);
   echo (“<br />”);
   echo ($item_desc . “</p>”);
   }
?>

When an option is sent from the JavaScript, the following happens:

  1. PHP finds out which RSS feed was selected
  2. An XML DOM object is created for the selected RSS feed
  3. The elements from the RSS channel are found and outputted
  4. Loops through the first three elements and output result

PHP Example – AJAX Poll



AJAX Poll

This example will demonstrate a poll where a web page can get results without reloading.

Do you like PHP and AJAX so far?

Yes:
No:


Example Explained – The HTML page

The HTML page contains a link to an external JavaScript, an HTML form, and a div element:

<html>
<head>
<script type=”text/javascript” src=”poll.js”></script>
</head>
<body>

<div id=”poll”>
<h3>Do you like PHP and AJAX so far?</h3>
<form>
Yes:
<input type=”radio” name=”vote” value=”0″ onclick=”getVote(this.value)” />
<br />No:
<input type=”radio” name=”vote” value=”1″ onclick=”getVote(this.value)” />
</form>
</div>

</body>
</html>

The HTML form works like this:

  1. An event is triggered when the user selects the “yes” or “no” option
  2. When the event is triggered, the function getVote() is executed
  3. The data returned from the getVote() function will replace the form, in the <div> tag

Example Explained – The JavaScript code

This is the JavaScript code stored in the file “poll.js”:

var xmlhttp;

function getVote(int)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
   {
   alert (“Browser does not support HTTP Request”);
   return;
   }
var url=”poll_vote.php”;
url=url+”?vote=”+int;
url=url+”&sid=”+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
   if (xmlhttp.readyState==4)
   {
   document.getElementById(“poll”).innerHTML=xmlHttp.responseText;
   }
}

function GetXmlHttpObject()
{
var objXMLHttp=null;
if (window.XMLHttpRequest)
   {
   objXMLHttp=new XMLHttpRequest();
   }
else if (window.ActiveXObject)
   {
   objXMLHttp=new ActiveXObject(“Microsoft.XMLHTTP”);
   }
return objXMLHttp;
}

The stateChanged() and GetXmlHttpObject functions are the same as in the PHP AJAX Suggest chapter.

The getVote() Function

This function executes when “yes” or “no” is selected in the HTML form.

  1. Calls the GetXmlHttpObject() function to create an XMLHTTP object
  2. Defines the URL (filename) to send to the server
  3. Adds a parameter (vote) to the URL with the content of the input field
  4. Adds a random number to prevent the server from using a cached file
  5. Each time the readyState property changes, the stateChanged() function will be executed
  6. Opens the XMLHTTP object with the given url.
  7. Sends an HTTP request to the server

The PHP Page

The server page called by the JavaScript code is a simple PHP file called “poll_vote.php”.

<?php
$vote = $_REQUEST['vote'];

//get content of textfile
$filename = “poll_result.txt”;
$content = file($filename);

//put content in array
$array = explode(“||”, $content[0]);
$yes = $array[0];
$no = $array[1];

if ($vote == 0)
   {
   $yes = $yes + 1;
   }
if ($vote == 1)
   {
   $no = $no + 1;
   }

//insert votes to txt file
$insertvote = $yes.”||”.$no;
$fp = fopen($filename,”w”);
fputs($fp,$insertvote);
fclose($fp);
?>

<h2>Result:</h2>
<table>
<tr>
<td>Yes:</td>
<td>
<img src=”poll.gif”
width=’<?php echo(100*round($yes/($no+$yes),2)); ?>’
height=’20′>
<?php echo(100*round($yes/($no+$yes),2)); ?>%
</td>
</tr>
<tr>
<td>No:</td>
<td>
<img src=”poll.gif”
width=’<?php echo(100*round($no/($no+$yes),2)); ?>’
height=’20′>
<?php echo(100*round($no/($no+$yes),2)); ?>%
</td>
</tr>
</table>

The selected value is sent from the JavaScript and the following happens:

  1. Get the content of the “poll_result.txt” file
  2. Put the content of the file in variables and add one to the selected variable
  3. Write the result to the “poll_result.txt” file
  4. Output a graphical representation of the poll result

The Text File

The text file (poll_result.txt) is where we store the data from the poll.

It is stored like this:

0||0

The first number represents the “Yes” votes, the second number represents the “No” votes.

Note: Remember to allow your web server to edit the text file. Do NOT give everyone access, just the web server (PHP).


PHP Array Functions



PHP Array Introduction

The array functions allow you to manipulate arrays.

PHP supports both simple and multi-dimensional arrays. There are also specific functions for populating arrays from database queries.


Installation

The array functions are part of the PHP core. There is no installation needed to use these functions.


PHP Array Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
array() Creates an array 3
array_change_key_case() Returns an array with all keys in lowercase or uppercase 4
array_chunk() Splits an array into chunks of arrays 4
array_combine() Creates an array by using one array for keys and another for its values 5
array_count_values() Returns an array with the number of occurrences for each value 4
array_diff() Compares array values, and returns the differences 4
array_diff_assoc() Compares array keys and values, and returns the differences 4
array_diff_key() Compares array keys, and returns the differences 5
array_diff_uassoc() Compares array keys and values, with an additional user-made function check, and returns the differences 5
array_diff_ukey() Compares array keys, with an additional user-made function check, and returns the differences 5
array_fill() Fills an array with values 4
array_filter() Filters elements of an array using a user-made function 4
array_flip() Exchanges all keys with their associated values in an array 4
array_intersect() Compares array values, and returns the matches 4
array_intersect_assoc() Compares array keys and values, and returns the matches 4
array_intersect_key() Compares array keys, and returns the matches 5
array_intersect_uassoc() Compares array keys and values, with an additional user-made function check, and returns the matches 5
array_intersect_ukey() Compares array keys, with an additional user-made function check, and returns the matches 5
array_key_exists() Checks if the specified key exists in the array 4
array_keys() Returns all the keys of an array 4
array_map() Sends each value of an array to a user-made function, which returns new values 4
array_merge() Merges one or more arrays into one array 4
array_merge_recursive() Merges one or more arrays into one array 4
array_multisort() Sorts multiple or multi-dimensional arrays 4
array_pad() Inserts a specified number of items, with a specified value, to an array 4
array_pop() Deletes the last element of an array 4
array_product() Calculates the product of the values in an array 5
array_push() Inserts one or more elements to the end of an array 4
array_rand() Returns one or more random keys from an array 4
array_reduce() Returns an array as a string, using a user-defined function 4
array_reverse() Returns an array in the reverse order 4
array_search() Searches an array for a given value and returns the key 4
array_shift() Removes the first element from an array, and returns the value of the removed element 4
array_slice() Returns selected parts of an array 4
array_splice() Removes and replaces specified elements of an array 4
array_sum() Returns the sum of the values in an array 4
array_udiff() Compares array values in a user-made function and returns an array 5
array_udiff_assoc() Compares array keys, and compares array values in a user-made function, and returns an array 5
array_udiff_uassoc() Compares array keys and array values in user-made functions, and returns an array 5
array_uintersect() Compares array values in a user-made function and returns an array 5
array_uintersect_assoc() Compares array keys, and compares array values in a user-made function, and returns an array 5
array_uintersect_uassoc() Compares array keys and array values in user-made functions, and returns an array 5
array_unique() Removes duplicate values from an array 4
array_unshift() Adds one or more elements to the beginning of an array 4
array_values() Returns all the values of an array 4
array_walk() Applies a user function to every member of an array 3
array_walk_recursive() Applies a user function recursively to every member of an array 5
arsort() Sorts an array in reverse order and maintain index association 3
asort() Sorts an array and maintain index association 3
compact() Create array containing variables and their values 4
count() Counts elements in an array, or properties in an object 3
current() Returns the current element in an array 3
each() Returns the current key and value pair from an array 3
end() Sets the internal pointer of an array to its last element 3
extract() Imports variables into the current symbol table from an array 3
in_array() Checks if a specified value exists in an array 4
key() Fetches a key from an array 3
krsort() Sorts an array by key in reverse order 3
ksort() Sorts an array by key 3
list() Assigns variables as if they were an array 3
natcasesort() Sorts an array using a case insensitive “natural order” algorithm 4
natsort() Sorts an array using a “natural order” algorithm 4
next() Advance the internal array pointer of an array 3
pos() Alias of current() 3
prev() Rewinds the internal array pointer 3
range() Creates an array containing a range of elements 3
reset() Sets the internal pointer of an array to its first element 3
rsort() Sorts an array in reverse order 3
shuffle() Shuffles an array 3
sizeof() Alias of count() 3
sort() Sorts an array 3
uasort() Sorts an array with a user-defined function and maintain index association 3
uksort() Sorts an array by keys using a user-defined function 3
usort() Sorts an array by values using a user-defined function 3

PHP Array Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
CASE_LOWER Used with array_change_key_case() to convert array keys to lower case  
CASE_UPPER Used with array_change_key_case() to convert array keys to upper case  
SORT_ASC Used with array_multisort() to sort in ascending order  
SORT_DESC Used with array_multisort() to sort in descending order  
SORT_REGULAR Used to compare items normally  
SORT_NUMERIC Used to compare items numerically  
SORT_STRING Used to compare items as strings  
SORT_LOCALE_STRING Used to compare items as strings, based on the current locale 4
COUNT_NORMAL    
COUNT_RECURSIVE    
EXTR_OVERWRITE    
EXTR_SKIP    
EXTR_PREFIX_SAME    
EXTR_PREFIX_ALL    
EXTR_PREFIX_INVALID    
EXTR_PREFIX_IF_EXISTS    
EXTR_IF_EXISTS    
EXTR_REFS    

PHP Calendar Functions



PHP Calendar Introduction

The calendar functions are useful when working with different calendar formats. The standard it is based on is the Julian day count (Julian day count is a count of days starting from January 1, 4713 B.C.). Note that the Julian day count is not the same as the Julian calendar!

Note: To convert between calendar formats, you must first convert to Julian day count, then to the calendar format.


Installation

The windows version of PHP has built-in support for the calendar extension. So, the calendar functions will work automatically.

However, if you are running the Linux version of PHP, you will have to compile PHP with –enable-calendar to get the calendar functions to work.


PHP Calendar Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
cal_days_in_month() Returns the number of days in a month for a specified year and calendar 4
cal_from_jd() Converts a Julian day count into a date of a specified calendar 4
cal_info() Returns information about a given calendar 4
cal_to_jd() Converts a date to Julian day count 4
easter_date() Returns the Unix timestamp for midnight on Easter of a specified year 3
easter_days() Returns the number of days after March 21, on which Easter falls for a specified year 3
FrenchToJD() Converts a French Republican date to a Julian day count 3
GregorianToJD() Converts a Gregorian date to a Julian day count 3
JDDayOfWeek() Returns the day of a week 3
JDMonthName() Returns a month name 3
JDToFrench() Converts a Julian day count to a French Republican date 3
JDToGregorian() Converts a Julian day count to a Gregorian date 3
jdtojewish() Converts a Julian day count to a Jewish date 3
JDToJulian() Converts a Julian day count to a Julian date 3
jdtounix() Converts a Julian day count to a Unix timestamp 4
JewishToJD() Converts a Jewish date to a Julian day count 3
JulianToJD() Converts a Julian date to a Julian day count 3
unixtojd() Converts a Unix timestamp to a Julian day count 4

PHP Calendar Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
CAL_GREGORIAN Gregorian calendar 3
CAL_JULIAN Julian calendar 3
CAL_JEWISH Jewish calendar 3
CAL_FRENCH French Republican calendar 3
CAL_NUM_CALS   3
CAL_DOW_DAYNO   3
CAL_DOW_SHORT   3
CAL_DOW_LONG   3
CAL_MONTH_GREGORIAN_SHORT   3
CAL_MONTH_GREGORIAN_LONG   3
CAL_MONTH_JULIAN_SHORT   3
CAL_MONTH_JULIAN_LONG   3
CAL_MONTH_JEWISH   3
CAL_MONTH_FRENCH   3
CAL_EASTER_DEFAULT   4
CAL_EASTER_DEFAULT   4
CAL_EASTER_ROMAN   4
CAL_EASTER_ALWAYS_GREGORIAN   4
CAL_EASTER_ALWAYS_JULIAN   4
CAL_JEWISH_ADD_ALAFIM_GERESH   5
CAL_JEWISH_ADD_ALAFIM   5
CAL_JEWISH_ADD_GERESHAYIM   5

PHP Date / Time Functions



PHP Date / Time Introduction

The date/time functions allow you to extract and format the date and time on the server.

Note: These functions depend on the locale settings of the server!


Installation

The date/time functions are part of the PHP core. There is no installation needed to use these functions.


Runtime Configuration

The behavior of the date/time functions is affected by settings in php.ini.

Date/Time configuration options:

Name Default Description Changeable
date.default_latitude  “31.7667″ Specifies the default latitude (available since PHP 5). This option is used by date_sunrise() and date_sunset() PHP_INI_ALL
date.default_longitude “35.2333″ Specifies the default longitude (available since PHP 5). This option is used by date_sunrise() and date_sunset() PHP_INI_ALL
date.sunrise_zenith “90.83″ Specifies the default sunrise zenith (available since PHP 5). This option is used by date_sunrise() and date_sunset() PHP_INI_ALL
date.sunset_zenith “90.83″ Specifies the default sunset zenith (available since PHP 5). This option is used by date_sunrise() and date_sunset() PHP_INI_ALL
date.timezone “” Specifies the default timezone (available since PHP 5.1) PHP_INI_ALL

PHP Date / Time Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
checkdate() Validates a Gregorian date 3
date_default_timezone_get() Returns the default time zone 5
date_default_timezone_set() Sets the default time zone 5
date_sunrise() Returns the time of sunrise for a given day / location 5
date_sunset() Returns the time of sunset for a given day / location 5
date() Formats a local time/date 3
getdate() Returns an array that contains date and time information for a Unix timestamp 3
gettimeofday() Returns an array that contains current time information 3
gmdate() Formats a GMT/UTC date/time 3
gmmktime() Returns the Unix timestamp for a GMT date 3
gmstrftime() Formats a GMT/UTC time/date according to locale settings 3
idate() Formats a local time/date as integer 5
localtime() Returns an array that contains the time components of a Unix timestamp 4
microtime() Returns the microseconds for the current time 3
mktime() Returns the Unix timestamp for a date 3
strftime() Formats a local time/date according to locale settings 3
strptime() Parses a time/date generated with strftime() 5
strtotime() Parses an English textual date or time into a Unix timestamp 3
time() Returns the current time as a Unix timestamp 3

PHP Date / Time Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
DATE_ATOM Atom (example: 2005-08-15T16:13:03+0000)  
DATE_COOKIE HTTP Cookies (example: Sun, 14 Aug 2005 16:13:03 UTC)  
DATE_ISO8601 ISO-8601 (example: 2005-08-14T16:13:03+0000)  
DATE_RFC822 RFC 822 (example: Sun, 14 Aug 2005 16:13:03 UTC)  
DATE_RFC850 RFC 850 (example: Sunday, 14-Aug-05 16:13:03 UTC)  
DATE_RFC1036 RFC 1036 (example: Sunday, 14-Aug-05 16:13:03 UTC)  
DATE_RFC1123 RFC 1123 (example: Sun, 14 Aug 2005 16:13:03 UTC)  
DATE_RFC2822 RFC 2822 (Sun, 14 Aug 2005 16:13:03 +0000)  
DATE_RSS RSS (Sun, 14 Aug 2005 16:13:03 UTC)  
DATE_W3C World Wide Web Consortium (example: 2005-08-14T16:13:03+0000)  

PHP Directory Functions



PHP Directory Introduction

The directory functions allow you to retrieve information about directories and their contents.


Installation

The directory functions are part of the PHP core. There is no installation needed to use these functions.


PHP Directory Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
chdir() Changes the current directory 3
chroot() Changes the root directory of the current process 4
dir() Opens a directory handle and returns an object 3
closedir() Closes a directory handle 3
getcwd() Returns the current directory 4
opendir() Opens a directory handle 3
readdir() Returns an entry from a directory handle 3
rewinddir() Resets a directory handle 3
scandir() Lists files and directories inside a specified path 5

PHP Directory Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
DIRECTORY_SEPARATOR   3
PATH_SEPARATOR   4

PHP Error and Logging Functions



PHP Error and Logging Introduction

The error and logging functions allows error handling and logging.

The error functions allow users to define error handling rules, and modify the way the errors can be logged.

The logging functions allow users to log applications and send log messages to email, system logs or other machines.


Installation

The error and logging functions are part of the PHP core. There is no installation needed to use these functions.


PHP Error and Logging Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
debug_backtrace() Generates a backtrace 4
debug_print_backtrace() Prints a backtrace 5
error_get_last() Gets the last error occurred 5
error_log() Sends an error to the server error-log, to a file or to a remote destination 4
error_reporting() Specifies which errors are reported 4
restore_error_handler() Restores the previous error handler 4
restore_exception_handler() Restores the previous exception handler 5
set_error_handler() Sets a user-defined function to handle errors 4
set_exception_handler() Sets a user-defined function to handle exceptions 5
trigger_error() Creates a user-defined error message 4
user_error() Alias of trigger_error() 4

PHP Error and Logging Constants

PHP: indicates the earliest version of PHP that supports the constant.

Value Constant Description PHP
1 E_ERROR Fatal run-time errors. Errors that cannot be recovered from. Execution of the script is halted  
2 E_WARNING Non-fatal run-time errors. Execution of the script is not halted  
4 E_PARSE Compile-time parse errors. Parse errors should only be generated by the parser  
8 E_NOTICE Run-time notices. The script found something that might be an error, but could also happen when running a script normally  
16 E_CORE_ERROR Fatal errors at PHP startup. This is like an E_ERROR in the PHP core 4
32 E_CORE_WARNING Non-fatal errors at PHP startup. This is like an E_WARNING in the PHP core 4
64 E_COMPILE_ERROR Fatal compile-time errors. This is like an E_ERROR generated by the Zend Scripting Engine 4
128 E_COMPILE_WARNING Non-fatal compile-time errors. This is like an E_WARNING generated by the Zend Scripting Engine 4
256 E_USER_ERROR Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error() 4
512 E_USER_WARNING Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error() 4
1024 E_USER_NOTICE User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error() 4
2048 E_STRICT Run-time notices. PHP suggest changes to your code to help interoperability and compatibility of the code 5
4096 E_RECOVERABLE_ERROR Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler()) 5
8191 E_ALL All errors and warnings, except of level E_STRICT 5

PHP Filesystem Functions



PHP Filesystem Introduction

The filesystem functions allow you to access and manipulate the filesystem.


Installation

The filesystem functions are part of the PHP core. There is no installation needed to use these functions.


Runtime Configuration

The behavior of the filesystem functions is affected by settings in php.ini.

Filesystem configuration options:

Name Default Description Changeable
allow_url_fopen “1″ Allows fopen()-type functions to work with URLs (available since PHP 4.0.4) PHP_INI_SYSTEM
user_agent NULL Defines the user agent for PHP to send (available since PHP 4.3) PHP_INI_ALL
default_socket_timeout “60″ Sets the default timeout, in seconds, for socket based streams (available since PHP 4.3) PHP_INI_ALL
from “” Defines the anonymous FTP password (your email address) PHP_INI_ALL
auto_detect_line_endings “0″ When set to “1″, PHP will examine the data read by fgets() and file() to see if it is using Unix, MS-Dos or Mac line-ending characters (available since PHP 4.3) PHP_INI_ALL

Unix / Windows Compatibility

When specifying a path on Unix platforms, the forward slash (/) is used as directory separator. However, on Windows platforms, both forward slash (/) and backslash (\) can be used.


PHP Filesystem Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
basename() Returns the filename component of a path 3
chgrp() Changes the file group 3
chmod() Changes the file mode 3
chown() Changes the file owner 3
clearstatcache() Clears the file status cache 3
copy() Copies a file 3
delete() See unlink() or unset()  
dirname() Returns the directory name component of a path 3
disk_free_space() Returns the free space of a directory 4
disk_total_space() Returns the total size of a directory 4
diskfreespace() Alias of disk_free_space() 3
fclose() Closes an open file 3
feof() Tests for end-of-file on an open file 3
fflush() Flushes buffered output to an open file 4
fgetc() Returns a character from an open file 3
fgetcsv() Parses a line from an open file, checking for CSV fields 3
fgets() Returns a line from an open file 3
fgetss() Returns a line, with HTML and PHP tags removed, from an open file 3
file() Reads a file into an array 3
file_exists() Checks whether or not a file or directory exists 3
file_get_contents() Reads a file into a string 4
file_put_contents Writes a string to a file 5
fileatime() Returns the last access time of a file 3
filectime() Returns the last change time of a file 3
filegroup() Returns the group ID of a file 3
fileinode() Returns the inode number of a file 3
filemtime() Returns the last modification time of a file 3
fileowner() Returns the user ID (owner) of a file 3
fileperms() Returns the permissions of a file 3
filesize() Returns the file size 3
filetype() Returns the file type 3
flock() Locks or releases a file 3
fnmatch() Matches a filename or string against a specified pattern 4
fopen() Opens a file or URL 3
fpassthru() Reads from an open file, until EOF, and writes the result to the output buffer 3
fputcsv() Formats a line as CSV and writes it to an open file 5
fputs() Alias of fwrite() 3
fread() Reads from an open file 3
fscanf() Parses input from an open file according to a specified format 4
fseek() Seeks in an open file 3
fstat() Returns information about an open file 4
ftell() Returns the current position in an open file 3
ftruncate() Truncates an open file to a specified length 4
fwrite() Writes to an open file 3
glob() Returns an array of filenames / directories matching a specified pattern 4
is_dir() Checks whether a file is a directory 3
is_executable() Checks whether a file is executable 3
is_file() Checks whether a file is a regular file 3
is_link() Checks whether a file is a link 3
is_readable() Checks whether a file is readable 3
is_uploaded_file() Checks whether a file was uploaded via HTTP POST 3
is_writable() Checks whether a file is writeable 4
is_writeable() Alias of is_writable() 3
link() Creates a hard link 3
linkinfo() Returns information about a hard link 3
lstat() Returns information about a file or symbolic link 3
mkdir() Creates a directory 3
move_uploaded_file() Moves an uploaded file to a new location 4
parse_ini_file() Parses a configuration file 4
pathinfo() Returns information about a file path 4
pclose() Closes a pipe opened by popen() 3
popen() Opens a pipe 3
readfile() Reads a file and writes it to the output buffer 3
readlink() Returns the target of a symbolic link 3
realpath() Returns the absolute pathname 4
rename() Renames a file or directory 3
rewind() Rewinds a file pointer 3
rmdir() Removes an empty directory 3
set_file_buffer() Sets the buffer size of an open file 3
stat() Returns information about a file 3
symlink() Creates a symbolic link 3
tempnam() Creates a unique temporary file 3
tmpfile() Creates a unique temporary file 3
touch() Sets access and modification time of a file 3
umask() Changes file permissions for files 3
unlink() Deletes a file 3

PHP Filesystem Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
GLOB_BRACE    
GLOB_ONLYDIR    
GLOB_MARK    
GLOB_NOSORT    
GLOB_NOCHECK    
GLOB_NOESCAPE    
PATHINFO_DIRNAME    
PATHINFO_BASENAME    
PATHINFO_EXTENSION    
FILE_USE_INCLUDE_PATH    
FILE_APPEND    
FILE_IGNORE_NEW_LINES    
FILE_SKIP_EMPTY_LINES    

PHP Filter Functions



PHP Filter Introduction

This PHP filters is used to validate and filter data coming from insecure sources, like user input.


Installation

The filter functions are part of the PHP core. There is no installation needed to use these functions.


PHP Filter Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
filter_has_var() Checks if a variable of a specified input type exist 5
filter_id() Returns the ID number of a specified filter 5
filter_input() Get input from outside the script and filter it 5
filter_input_array() Get multiple inputs from outside the script and filters them 5
filter_list() Returns an array of all supported filters 5
filter_var_array() Get multiple variables and filter them 5
filter_var() Get a variable and filter it 5

PHP Filters

ID Name Description
FILTER_CALLBACK Call a user-defined function to filter data
FILTER_SANITIZE_STRING Strip tags, optionally strip or encode special characters
FILTER_SANITIZE_STRIPPED Alias of “string” filter
FILTER_SANITIZE_ENCODED URL-encode string, optionally strip or encode special characters
FILTER_SANITIZE_SPECIAL_CHARS HTML-escape ‘”<>& and characters with ASCII value less than 32
FILTER_SANITIZE_EMAIL Remove all characters, except letters, digits and !#$%&’*+-/=?^_`{|}~@.[]
FILTER_SANITIZE_URL Remove all characters, except letters, digits and $-_.+!*’(),{}|\\^~[]`<>#%”;/?:@&=
FILTER_SANITIZE_NUMBER_INT Remove all characters, except digits and +-
FILTER_SANITIZE_NUMBER_FLOAT Remove all characters, except digits, +- and optionally .,eE
FILTER_SANITIZE_MAGIC_QUOTES Apply addslashes()
FILTER_UNSAFE_RAW Do nothing, optionally strip or encode special characters
FILTER_VALIDATE_INT Validate value as integer, optionally from the specified range
FILTER_VALIDATE_BOOLEAN Return TRUE for “1″, “true”, “on” and “yes”, FALSE for “0″, “false”, “off”, “no”, and “”, NULL otherwise
FILTER_VALIDATE_FLOAT Validate value as float
FILTER_VALIDATE_REGEXP Validate value against regexp, a Perl-compatible regular expression
FILTER_VALIDATE_URL Validate value as URL, optionally with required components
FILTER_VALIDATE_EMAIL Validate value as e-mail
FILTER_VALIDATE_IP Validate value as IP address, optionally only IPv4 or IPv6 or not from private or reserved ranges

PHP FTP Functions



PHP FTP Introduction

The FTP functions give client access to file servers through the File Transfer Protocol (FTP).

The FTP functions are used to open, login and close connections, as well as upload, download, rename, delete, and get information on files from file servers. Not all of the FTP functions will work with every server or return the same results. The FTP functions became available with PHP 3.

These functions are meant for detailed access to an FTP server. If you only wish to read from or write to a file on an FTP server, consider using the ftp:// wrapper with the Filesystem functions.


Installation

The windows version of PHP has built-in support for the FTP extension. So, the FTP functions will work automatically.

However, if you are running the Linux version of PHP, you will have to compile PHP with –enable-ftp (PHP 4+) or –with-ftp (PHP 3) to get the FTP functions to work.


PHP FTP Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
ftp_alloc() Allocates space for a file to be uploaded to the FTP server 5
ftp_cdup() Changes the current directory to the parent directory on the FTP server 3
ftp_chdir() Changes the current directory on the FTP server 3
ftp_chmod() Sets permissions on a file via FTP 5
ftp_close() Closes an FTP connection 4
ftp_connect() Opens an FTP connection 3
ftp_delete() Deletes a file on the FTP server 3
ftp_exec() Executes a program/command on the FTP server 4
ftp_fget() Downloads a file from the FTP server and saves it to an open file 3
ftp_fput() Uploads from an open file and saves it to a file on the FTP server 3
ftp_get_option() Returns runtime behaviors of the FTP connection 4
ftp_get() Downloads a file from the FTP server 3
ftp_login() Logs on to an FTP connection 3
ftp_mdtm() Returns the last modified time of a specified file 3
ftp_mkdir() Creates a new directory on the FTP server 3
ftp_nb_continue() Continues retrieving/sending a file (non-blocking) 4
ftp_nb_fget() Downloads a file from the FTP server and saves it to an open file (non-blocking) 4
ftp_nb_fput() Uploads from an open file and saves it to a file on the FTP server (non-blocking) 4
ftp_nb_get() Downloads a file from the FTP server (non-blocking) 4
ftp_nb_put() Uploads a file to the FTP server (non-blocking) 4
ftp_nlist() Lists the files in a specified directory on the FTP server 3
ftp_pasv() Turns passive mode on or off 3
ftp_put() Uploads a file to the FTP server 3
ftp_pwd() Returns the current directory name 3
ftp_quit() Alias of ftp_close() 3
ftp_raw() Sends a raw command to the FTP server 5
ftp_rawlist() Returns a detailed list of files in the specified directory 3
ftp_rename() Renames a file or directory on the FTP server 3
ftp_rmdir() Removes a directory on the FTP server 3
ftp_set_option() Sets runtime options for the FTP connection 4
ftp_site() Sends a SITE command to the server 3
ftp_size() Returns the size of the specified file 3
ftp_ssl_connect() Opens a secure SSL-FTP connection 4
ftp_systype() Returns the system type identifier of the FTP server 3

PHP FTP Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
FTP_ASCII   3
FTP_TEXT   3
FTP_BINARY   3
FTP_IMAGE   3
FTP_TIMEOUT_SEC   3
FTP_AUTOSEEK   4
FTP_AUTORESUME Determine resume position and start position for get and put requests automatically 4
FTP_FAILED Asynchronous transfer has failed 4
FTP_FINISHED Asynchronous transfer has finished 4
FTP_MOREDATA Asynchronous transfer is still active 4

PHP HTTP Functions



PHP HTTP Introduction

The HTTP functions let you manipulate information sent to the browser by the Web server, before any other output has been sent.


Installation

The directory functions are part of the PHP core. There is no installation needed to use these functions.


PHP HTTP Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
header() Sends a raw HTTP header to a client 3
headers_list() Returns a list of response headers sent (or ready to send) 5
headers_sent() Checks if / where the HTTP headers have been sent 3
setcookie() Sends an HTTP cookie to a client 3
setrawcookie() Sends an HTTP cookie without URL encoding the cookie value 5

PHP HTTP Constants

None.


PHP libxml Functions



PHP libxml Introduction

The libxml functions and constants are used together with SimpleXML, XSLT and DOM functions.


Installation

These functions require the libxml package. Download at xmlsoft.org


PHP libxml Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
libxml_clear_errors() Clear libxml error buffer 5
libxml_get_errors() Retrieve array of errors 5
libxml_get_last_error() Retrieve last error from libxml 5
libxml_set_streams_context() Set the streams context for the next libxml document load or write 5
libxml_use_internal_errors() Disable libxml errors and allow user to fetch error information as needed 5

PHP libxml Constants

Function Description PHP
LIBXML_COMPACT Set small nodes allocation optimization. This may improve the application performance 5
LIBXML_DTDATTR Set default DTD attributes 5
LIBXML_DTDLOAD Load external subset 5
LIBXML_DTDVALID Validate with the DTD 5
LIBXML_NOBLANKS Remove blank nodes 5
LIBXML_NOCDATA Set CDATA as text nodes 5
LIBXML_NOEMPTYTAG Change empty tags (e.g. <br/> to <br></br>), only available in the DOMDocument->save() and DOMDocument->saveXML() functions 5
LIBXML_NOENT Substitute entities 5
LIBXML_NOERROR Do not show error reports 5
LIBXML_NONET Stop network access while loading documents 5
LIBXML_NOWARNING Do not show warning reports 5
LIBXML_NOXMLDECL Drop the XML declaration when saving a document 5
LIBXML_NSCLEAN Remove excess namespace declarations 5
LIBXML_XINCLUDE Use XInclude substitution 5
LIBXML_ERR_ERROR Get recoverable errors 5
LIBXML_ERR_FATAL Get fatal errors 5
LIBXML_ERR_NONE Get no errors 5
LIBXML_ERR_WARNING Get simple warnings 5
LIBXML_VERSION Get libxml version (e.g. 20605 or 20617) 5
LIBXML_DOTTED_VERSION Get dotted libxml version (e.g. 2.6.5 or 2.6.17) 5

PHP Mail Functions



PHP Mail Introduction

The mail() function allows you to send emails directly from a script.


Requirements

For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file.


Installation

The mail functions are part of the PHP core. There is no installation needed to use these functions.


Runtime Configuration

The behavior of the mail functions is affected by settings in the php.ini file.

Mail configuration options:

Name Default Description Changeable
SMTP “localhost” Windows only: The DNS name or IP address of the SMTP server PHP_INI_ALL
smtp_port “25″ Windows only: The SMTP port number. Available since PHP 4.3 PHP_INI_ALL
sendmail_from NULL Windows only: Specifies the “from” address to be used in email sent from PHP PHP_INI_ALL
sendmail_path NULL Unix systems only: Specifies where the sendmail program can be found (usually /usr/sbin/sendmail or /usr/lib/sendmail) PHP_INI_SYSTEM

PHP Mail Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
ezmlm_hash() Calculates the hash value needed by the EZMLM mailing list system 3
mail() Allows you to send emails directly from a script 3

PHP Mail Constants

None.


PHP Math Functions



PHP Math Introduction

The math functions can handle values within the range of integer and float types.


Installation

The math functions are part of the PHP core. There is no installation needed to use these functions.


PHP Math Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
abs() Returns the absolute value of a number 3
acos() Returns the arccosine of a number 3
acosh() Returns the inverse hyperbolic cosine of a number 4
asin() Returns the arcsine of a number 3
asinh() Returns the inverse hyperbolic sine of a number 4
atan() Returns the arctangent of a number as a numeric value between -PI/2 and PI/2 radians 3
atan2() Returns the angle theta of an (x,y) point as a numeric value between -PI and PI radians 3
atanh() Returns the inverse hyperbolic tangent of a number 4
base_convert() Converts a number from one base to another 3
bindec() Converts a binary number to a decimal number 3
ceil() Returns the value of a number rounded upwards to the nearest integer 3
cos() Returns the cosine of a number 3
cosh() Returns the hyperbolic cosine of a number 4
decbin() Converts a decimal number to a binary number 3
dechex() Converts a decimal number to a hexadecimal number 3
decoct() Converts a decimal number to an octal number 3
deg2rad() Converts a degree to a radian number 3
exp() Returns the value of Ex 3
expm1() Returns the value of Ex – 1 4
floor() Returns the value of a number rounded downwards to the nearest integer 3
fmod() Returns the remainder (modulo) of the division of the arguments 4
getrandmax() Returns the maximum random number that can be returned by a call to the rand() function 3
hexdec() Converts a hexadecimal number to a decimal number 3
hypot() Returns the length of the hypotenuse of a right-angle triangle 4
is_finite() Returns true if a value is a finite number 4
is_infinite() Returns true if a value is an infinite number 4
is_nan() Returns true if a value is not a number 4
lcg_value() Returns a pseudo random number in the range of (0,1) 4
log() Returns the natural logarithm (base E) of a number 3
log10() Returns the base-10 logarithm of a number 3
log1p() Returns log(1+number) 4
max() Returns the number with the highest value of two specified numbers 3
min() Returns the number with the lowest value of two specified numbers 3
mt_getrandmax() Returns the largest possible value that can be returned by mt_rand() 3
mt_rand() Returns a random integer using Mersenne Twister algorithm 3
mt_srand() Seeds the Mersenne Twister random number generator 3
octdec() Converts an octal number to a decimal number 3
pi() Returns the value of PI 3
pow() Returns the value of x to the power of y 3
rad2deg() Converts a radian number to a degree 3
rand() Returns a random integer 3
round() Rounds a number to the nearest integer 3
sin() Returns the sine of a number 3
sinh() Returns the hyperbolic sine of a number 4
sqrt() Returns the square root of a number 3
srand() Seeds the random number generator 3
tan() Returns the tangent of an angle 3
tanh() Returns the hyperbolic tangent of an angle 4

PHP Math Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
M_E Returns e (approx. 2.718) 4
M_EULER Returns Euler’s constant (approx. 0.577) 4
M_LNPI Returns the natural logarithm of PI (approx. 1.144) 4
M_LN2 Returns the natural logarithm of 2 (approx. 0.693) 4
M_LN10 Returns the natural logarithm of 10 (approx. 2.302) 4
M_LOG2E Returns the base-2 logarithm of E (approx. 1.442) 4
M_LOG10E Returns the base-10 logarithm of E (approx. 0.434) 4
M_PI Returns PI (approx. 3.14159) 3
M_PI_2 Returns PI/2 (approx. 1.570) 4
M_PI_4 Returns PI/4 (approx. 0.785) 4
M_1_PI Returns 1/PI (approx. 0.318) 4
M_2_PI Returns 2/PI (approx. 0.636) 4
M_SQRTPI Returns the square root of PI (approx. 1.772) 4
M_2_SQRTPI Returns 2/square root of PI (approx. 1.128) 4
M_SQRT1_2 Returns the square root of 1/2 (approx. 0.707) 4
M_SQRT2 Returns the square root of 2 (approx. 1.414) 4
M_SQRT3 Returns the square root of 3 (approx. 1.732) 4

PHP Misc. Functions



PHP Miscellaneous Introduction

The misc. functions were only placed here because none of the other categories seemed to fit.


Installation

The misc functions are part of the PHP core. There is no installation needed to use these functions.


Runtime Configuration

The behavior of the misc functions is affected by settings in the php.ini file.

Misc. configuration options:

Name Default Description Changeable
ignore_user_abort “0″ FALSE indicates that scripts will be terminated as soon as they try to output something after a client has aborted their connection PHP_INI_ALL
highlight.string “#DD0000″ Color for highlighting a string in PHP syntax PHP_INI_ALL
highlight.comment “#FF8000″ Color for highlighting PHP comments PHP_INI_ALL
highlight.keyword “#007700″ Color for syntax highlighting PHP keywords (e.g. parenthesis and semicolon) PHP_INI_ALL
highlight.bg “#FFFFFF” Color for background PHP_INI_ALL
highlight.default “#0000BB” Default color for PHP syntax PHP_INI_ALL
highlight.html “#000000″ Color for HTML code PHP_INI_ALL
browscap NULL Name and location of browser-capabilities file (e.g. browscap.ini) PHP_INI_SYSTEM

PHP Misc. Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
connection_aborted() Checks whether the client has disconnected 3
connection_status() Returns the current connection status 3
connection_timeout() Deprecated in PHP 4.0.5 3
constant() Returns the value of a constant 4
define() Defines a constant 3
defined() Checks whether a constant exists 3
die() Prints a message and exits the current script 3
eval() Evaluates a string as PHP code 3
exit() Prints a message and exits the current script 3
get_browser() Returns the capabilities of the user’s browser 3
highlight_file() Outputs a file with the PHP syntax highlighted 4
highlight_string() Outputs a string with the PHP syntax highlighted 4
ignore_user_abort() Sets whether a remote client can abort the running of a script 3
pack() Packs data into a binary string 3
php_check_syntax() Deprecated in PHP 5.0.5 5
php_strip_whitespace() Returns the source code of a file with PHP comments and whitespace removed 5
show_source() Alias of highlight_file() 4
sleep() Delays code execution for a number of seconds 3
time_nanosleep() Delays code execution for a number of seconds and nanoseconds 5
time_sleep_until() Delays code execution until a specified time 5
uniqid() Generates a unique ID 3
unpack() Unpacks data from a binary string 3
usleep() Delays code execution for a number of microseconds 3

PHP Misc. Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
CONNECTION_ABORTED    
CONNECTION_NORMAL    
CONNECTION_TIMEOUT    
__COMPILER_HALT_OFFSET__   5

PHP MySQL Functions



PHP MySQL Introduction

The MySQL functions allows you to access MySQL database servers.


Installation

For the MySQL functions to be available, you must compile PHP with MySQL support.

For compiling, use –with-mysql=DIR (the optional DIR points to the MySQL directory).

Note: For full functionality of MySQL versions greater than 4.1., use the MySQLi extension instead. If you would like to install both the mysql extension and the mysqli extension you should use the same client library to avoid any conflicts.

Installation on Linux Systems

PHP 5+: MySQL and the MySQL library is not enabled by default. Use the –with-mysql=DIR configure option to include MySQL support and download headers and libraries from www.mysql.com.

Installation on Windows Systems

PHP 5+: MySQL is not enabled by default, so the php_mysql.dll must be enabled inside of php.ini. Also, PHP needs access to the MySQL client library. A file named libmysql.dll is included in the Windows PHP distribution, and in order for PHP to talk to MySQL this file needs to be available to the Windows systems PATH.

To enable any PHP extension, the PHP extension_dir setting (in the php.ini file) should be set to the directory where the PHP extensions are located. An example extension_dir value is c:\php\ext.

Note: If you get the following error when starting the web server: “Unable to load dynamic library ‘./php_mysql.dll’”, this is because php_mysql.dll or libmysql.dll cannot be found by the system.


Runtime Configuration

The behavior of the MySQL functions is affected by settings in the php.ini file.

MySQL configuration options:

Name Default Description Changeable
mysql.allow_persistent “1″ Whether or not to allow persistent connections PHP_INI_SYSTEM
mysql.max_persistent “-1″ The maximum number of persistent connections per process PHP_INI_SYSTEM
mysql.max_links “-1″ The maximum number of connections per process (persistent connections included) PHP_INI_SYSTEM
mysql.trace_mode “0″ Trace mode. When set to “1″, warnings and SQL-errors will be displayed. Available since PHP 4.3 PHP_INI_ALL
mysql.default_port NULL The default TCP port number to use PHP_INI_ALL
mysql.default_socket NULL The default socket name to use. Available since PHP 4.0.1 PHP_INI_ALL
mysql.default_host NULL The default server host to use (doesn’t apply in SQL safe mode) PHP_INI_ALL
mysql.default_user NULL The default user name to use (doesn’t apply in SQL safe mode) PHP_INI_ALL
mysql.default_password NULL The default password to use (doesn’t apply in SQL safe mode) PHP_INI_ALL
mysql.connect_timeout “60″ Connection timeout in seconds PHP_INI_ALL

Resource Types

There are two resource types used in the MySQL extension. The first one is the link_identifier for a database connection, the second is a resource which holds the result of a query.

Note: Most MySQL functions accept link_identifier as the last optional parameter. If it is not provided, the last opened connection is used.


PHP MySQL Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
mysql_affected_rows() Returns the number of affected rows in the previous MySQL operation 3
mysql_change_user() Deprecated. Changes the user of the current MySQL connection 3
mysql_client_encoding() Returns the name of the character set for the current connection 4
mysql_close() Closes a non-persistent MySQL connection 3
mysql_connect() Opens a non-persistent MySQL connection 3
mysql_create_db() Deprecated. Creates a new MySQL database. Use mysql_query() instead 3
mysql_data_seek() Moves the record pointer 3
mysql_db_name() Returns a database name from a call to mysql_list_dbs() 3
mysql_db_query() Deprecated. Sends a MySQL query. Use mysql_select_db() and mysql_query() instead 3
mysql_drop_db() Deprecated. Deletes a MySQL database. Use mysql_query() instead 3
mysql_errno() Returns the error number of the last MySQL operation 3
mysql_error() Returns the error description of the last MySQL operation 3
mysql_escape_string() Deprecated. Escapes a string for use in a mysql_query. Use mysql_real_escape_string() instead 4
mysql_fetch_array() Returns a row from a recordset as an associative array and/or a numeric array 3
mysql_fetch_assoc() Returns a row from a recordset as an associative array 4
mysql_fetch_field() Returns column info from a recordset as an object 3
mysql_fetch_lengths() Returns the length of the contents of each field in a result row 3
mysql_fetch_object() Returns a row from a recordset as an object 3
mysql_fetch_row() Returns a row from a recordset as a numeric array 3
mysql_field_flags() Returns the flags associated with a field in a recordset 3
mysql_field_len() Returns the maximum length of a field in a recordset 3
mysql_field_name() Returns the name of a field in a recordset 3
mysql_field_seek() Moves the result pointer to a specified field 3
mysql_field_table() Returns the name of the table the specified field is in 3
mysql_field_type() Returns the type of a field in a recordset 3
mysql_free_result() Free result memory 3
mysql_get_client_info() Returns MySQL client info 4
mysql_get_host_info() Returns MySQL host info 4
mysql_get_proto_info() Returns MySQL protocol info 4
mysql_get_server_info() Returns MySQL server info 4
mysql_info() Returns information about the last query 4
mysql_insert_id() Returns the AUTO_INCREMENT ID generated from the previous INSERT operation 3
mysql_list_dbs() Lists available databases on a MySQL server 3
mysql_list_fields() Deprecated. Lists MySQL table fields. Use mysql_query() instead 3
mysql_list_processes() Lists MySQL processes 4
mysql_list_tables() Deprecated. Lists tables in a MySQL database. Use mysql_query() instead 3
mysql_num_fields() Returns the number of fields in a recordset 3
mysql_num_rows() Returns the number of rows in a recordset 3
mysql_pconnect() Opens a persistent MySQL connection 3
mysql_ping() Pings a server connection or reconnects if there is no connection 4
mysql_query() Executes a query on a MySQL database 3
mysql_real_escape_string() Escapes a string for use in SQL statements 4
mysql_result() Returns the value of a field in a recordset 3
mysql_select_db() Sets the active MySQL database 3
mysql_stat() Returns the current system status of the MySQL server 4
mysql_tablename() Deprecated. Returns the table name of field. Use mysql_query() instead 3
mysql_thread_id() Returns the current thread ID 4
mysql_unbuffered_query() Executes a query on a MySQL database (without fetching / buffering the result) 4

PHP MySQL Constants

Since PHP 4.3 it has been possible to specify additional flags for the mysql_connect() and mysql_pconnect() functions:

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
MYSQL_CLIENT_COMPRESS Use compression protocol 4.3
MYSQL_CLIENT_IGNORE_SPACE Allow space after function names 4.3
MYSQL_CLIENT_INTERACTIVE Allow interactive timeout seconds of inactivity before closing the connection 4.3
MYSQL_CLIENT_SSL Use SSL encryption (only available with version 4+ of the MySQL client library) 4.3

The mysql_fetch_array() function uses a constant for the different types of result arrays. The following constants are defined:

Constant Description PHP
MYSQL_ASSOC Columns are returned into the array with the fieldname as the array index  
MYSQL_BOTH Columns are returned into the array having both a numerical index and the fieldname as the array index  
MYSQL_NUM Columns are returned into the array having a numerical index (index starts at 0)  

PHP SimpleXML Functions



PHP SimpleXML Introduction

The SimpleXML functions lets you convert XML to an object.

This object can be processed, like any other object, with normal property selectors and array iterators.

Some of these functions requires the newest PHP build.


Installation

The SimpleXML functions are part of the PHP core. There is no installation needed to use these functions.


PHP SimpleXML Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
__construct() Creates a new SimpleXMLElement object 5
addAttribute() Adds an attribute to the SimpleXML element 5
addChild() Adds a child element the SimpleXML element 5
asXML() Gets an XML string from a SimpleXML element 5
attributes() Gets a SimpleXML element’s attributes 5
children() Gets the children of a specified node 5
getDocNamespaces() Gets the namespaces of an XML document 5
getName() Gets the name of a SimpleXML element 5
getNamespaces() Gets the namespaces from XML data 5
registerXPathNamespace() Creates a namespace context for the next XPath query 5
simplexml_import_dom() Gets a SimpleXMLElement object from a DOM node 5
simplexml_load_file() Gets a SimpleXMLElement object from an XML document 5
simplexml_load_string() Gets a SimpleXMLElement object from an XML string 5
xpath() Runs an XPath query on XML data 5

PHP SimpleXML Constants

None



PHP String Functions



PHP String Introduction

The string functions allow you to manipulate strings.


Installation

The string functions are part of the PHP core. There is no installation needed to use these functions.


PHP String Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
addcslashes() Returns a string with backslashes in front of the specified characters 4
addslashes() Returns a string with backslashes in front of predefined characters 3
bin2hex() Converts a string of ASCII characters to hexadecimal values 3
chop() Alias of rtrim() 3
chr() Returns a character from a specified ASCII value 3
chunk_split() Splits a string into a series of smaller parts 3
convert_cyr_string() Converts a string from one Cyrillic character-set to another 3
convert_uudecode() Decodes a uuencoded string 5
convert_uuencode() Encodes a string using the uuencode algorithm 5
count_chars() Returns how many times an ASCII character occurs within a string and returns the information 4
crc32() Calculates a 32-bit CRC for a string 4
crypt() One-way string encryption (hashing) 3
echo() Outputs strings 3
explode() Breaks a string into an array 3
fprintf() Writes a formatted string to a specified output stream 5
get_html_translation_table() Returns the translation table used by htmlspecialchars() and htmlentities() 4
hebrev() Converts Hebrew text to visual text 3
hebrevc() Converts Hebrew text to visual text and new lines (\n) into <br /> 3
html_entity_decode() Converts HTML entities to characters 4
htmlentities() Converts characters to HTML entities 3
htmlspecialchars_decode() Converts some predefined HTML entities to characters 5
htmlspecialchars() Converts some predefined characters to HTML entities 3
implode() Returns a string from the elements of an array 3
join() Alias of implode() 3
levenshtein() Returns the Levenshtein distance between two strings 3
localeconv() Returns locale numeric and monetary formatting information 4
ltrim() Strips whitespace from the left side of a string 3
md5() Calculates the MD5 hash of a string 3
md5_file() Calculates the MD5 hash of a file 4
metaphone() Calculates the metaphone key of a string 4
money_format() Returns a string formatted as a currency string 4
nl_langinfo() Returns specific local information 4
nl2br() Inserts HTML line breaks in front of each newline in a string 3
number_format() Formats a number with grouped thousands 3
ord() Returns the ASCII value of the first character of a string 3
parse_str() Parses a query string into variables 3
print() Outputs a string 3
printf() Outputs a formatted string 3
quoted_printable_decode() Decodes a quoted-printable string 3
quotemeta() Quotes meta characters 3
rtrim() Strips whitespace from the right side of a string 3
setlocale() Sets locale information 3
sha1() Calculates the SHA-1 hash of a string 4
sha1_file() Calculates the SHA-1 hash of a file 4
similar_text() Calculates the similarity between two strings 3
soundex() Calculates the soundex key of a string 3
sprintf() Writes a formatted string to a variable 3
sscanf() Parses input from a string according to a format 4
str_ireplace() Replaces some characters in a string (case-insensitive) 5
str_pad() Pads a string to a new length 4
str_repeat() Repeats a string a specified number of times 4
str_replace() Replaces some characters in a string (case-sensitive) 3
str_rot13() Performs the ROT13 encoding on a string 4
str_shuffle() Randomly shuffles all characters in a string 4
str_split() Splits a string into an array 5
str_word_count() Count the number of words in a string 4
strcasecmp() Compares two strings (case-insensitive) 3
strchr() Finds the first occurrence of a string inside another string (alias of strstr()) 3
strcmp() Compares two strings (case-sensitive) 3
strcoll() Locale based string comparison 4
strcspn() Returns the number of characters found in a string before any part of some specified characters are found 3
strip_tags() Strips HTML and PHP tags from a string 3
stripcslashes() Unquotes a string quoted with addcslashes() 4
stripslashes() Unquotes a string quoted with addslashes() 3
stripos() Returns the position of the first occurrence of a string inside another string (case-insensitive) 5
stristr() Finds the first occurrence of a string inside another string (case-insensitive) 3
strlen() Returns the length of a string 3
strnatcasecmp() Compares two strings using a “natural order” algorithm (case-insensitive) 4
strnatcmp() Compares two strings using a “natural order” algorithm (case-sensitive) 4
strncasecmp() String comparison of the first n characters (case-insensitive) 4
strncmp() String comparison of the first n characters (case-sensitive) 4
strpbrk() Searches a string for any of a set of characters 5
strpos() Returns the position of the first occurrence of a string inside another string (case-sensitive) 3
strrchr() Finds the last occurrence of a string inside another string 3
strrev() Reverses a string 3
strripos() Finds the position of the last occurrence of a string inside another string (case-insensitive) 5
strrpos() Finds the position of the last occurrence of a string inside another string (case-sensitive) 3
strspn() Returns the number of characters found in a string that contains only characters from a specified charlist 3
strstr() Finds the first occurrence of a string inside another string (case-sensitive) 3
strtok() Splits a string into smaller strings 3
strtolower() Converts a string to lowercase letters 3
strtoupper() Converts a string to uppercase letters 3
strtr() Translates certain characters in a string 3
substr() Returns a part of a string 3
substr_compare() Compares two strings from a specified start position (binary safe and optionally case-sensitive) 5
substr_count() Counts the number of times a substring occurs in a string 4
substr_replace() Replaces a part of a string with another string 4
trim() Strips whitespace from both sides of a string 3
ucfirst() Converts the first character of a string to uppercase 3
ucwords() Converts the first character of each word in a string to uppercase 3
vfprintf() Writes a formatted string to a specified output stream 5
vprintf() Outputs a formatted string 4
vsprintf() Writes a formatted string to a variable 4
wordwrap() Wraps a string to a given number of characters 4

PHP String Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
CRYPT_SALT_LENGTH Contains the length of the default encryption method for the
system. For standard DES encryption, the length is 2
 
CRYPT_STD_DES Set to 1 if the standard DES-based encryption with a 2 character salt is supported, 0 otherwise  
CRYPT_EXT_DES Set to 1 if the extended DES-based encryption with a 9 character salt is supported, 0 otherwise  
CRYPT_MD5 Set to 1 if the MD5 encryption with a 12 character salt starting with $1$ is supported, 0 otherwise  
CRYPT_BLOWFISH Set to 1 if the Blowfish encryption with a 16 character salt starting with $2$ or $2a$ is supported, 0 otherwise0  
HTML_SPECIALCHARS    
HTML_ENTITIES    
ENT_COMPAT    
ENT_QUOTES    
ENT_NOQUOTES    
CHAR_MAX    
LC_CTYPE    
LC_NUMERIC    
LC_TIME    
LC_COLLATE    
LC_MONETARY    
LC_ALL    
LC_MESSAGES    
STR_PAD_LEFT    
STR_PAD_RIGHT    
STR_PAD_BOTH    

PHP XML Parser Functions



PHP XML Parser Introduction

The XML functions lets you parse, but not validate, XML documents.

XML is a data format for standardized structured document exchange. More information on XML can be found in our XML Tutorial.

This extension uses the Expat XML parser.

Expat is an event-based parser, it views an XML document as a series of events. When an event occurs, it calls a specified function to handle it.

Expat is a non-validating parser, and ignores any DTDs linked to a document. However, if the document is not well formed it will end with an error message.

Because it is an event-based, non validating parser, Expat is fast and well suited for web applications.

The XML parser functions lets you create XML parsers and define handlers for XML events.


Installation

The XML functions are part of the PHP core. There is no installation needed to use these functions.


PHP XML Parser Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
utf8_decode() Decodes an UTF-8 string to ISO-8859-1 3
utf8_encode() Encodes an ISO-8859-1 string to UTF-8 3
xml_error_string() Gets an error string from the XML parser 3
xml_get_current_byte_index() Gets the current byte index from the XML parser 3
xml_get_current_column_number() Gets the current column number from the XML parser 3
xml_get_current_line_number() Gets the current line number from the XML parser 3
xml_get_error_code() Gets an error code from the XML parser 3
xml_parse() Parses an XML document 3
xml_parse_into_struct() Parse XML data into an array 3
xml_parser_create_ns() Create an XML parser with namespace support 4
xml_parser_create() Create an XML parser 3
xml_parser_free() Free an XML parser 3
xml_parser_get_option() Get options from an XML parser 3
xml_parser_set_option() Set options in an XML parser 3
xml_set_character_data_handler() Set handler function for character data 3
xml_set_default_handler() Set default handler function 3
xml_set_element_handler() Set handler function for start and end element of elements 3
xml_set_end_namespace_decl_handler() Set handler function for the end of namespace declarations 4
xml_set_external_entity_ref_handler() Set handler function for external entities 3
xml_set_notation_decl_handler() Set handler function for notation declarations 3
xml_set_object() Use XML Parser within an object 4
xml_set_processing_instruction_handler() Set handler function for processing instruction 3
xml_set_start_namespace_decl_handler() Set handler function for the start of namespace declarations 4
xml_set_unparsed_entity_decl_handler() Set handler function for unparsed entity declarations 3

PHP XML Parser Constants

Constant
XML_ERROR_NONE (integer)
XML_ERROR_NO_MEMORY (integer)
XML_ERROR_SYNTAX (integer)
XML_ERROR_NO_ELEMENTS (integer)
XML_ERROR_INVALID_TOKEN (integer)
XML_ERROR_UNCLOSED_TOKEN (integer)
XML_ERROR_PARTIAL_CHAR (integer)
XML_ERROR_TAG_MISMATCH (integer)
XML_ERROR_DUPLICATE_ATTRIBUTE (integer)
XML_ERROR_JUNK_AFTER_DOC_ELEMENT (integer)
XML_ERROR_PARAM_ENTITY_REF (integer)
XML_ERROR_UNDEFINED_ENTITY (integer)
XML_ERROR_RECURSIVE_ENTITY_REF (integer)
XML_ERROR_ASYNC_ENTITY (integer)
XML_ERROR_BAD_CHAR_REF (integer)
XML_ERROR_BINARY_ENTITY_REF (integer)
XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF (integer)
XML_ERROR_MISPLACED_XML_PI (integer)
XML_ERROR_UNKNOWN_ENCODING (integer)
XML_ERROR_INCORRECT_ENCODING (integer)
XML_ERROR_UNCLOSED_CDATA_SECTION (integer)
XML_ERROR_EXTERNAL_ENTITY_HANDLING (integer)
XML_OPTION_CASE_FOLDING (integer)
XML_OPTION_TARGET_ENCODING (integer)
XML_OPTION_SKIP_TAGSTART (integer)
XML_OPTION_SKIP_WHITE (integer)

PHP Zip File Functions



PHP Zip File Introduction

The Zip files functions allows you to read ZIP files.


Installation

For the Zip file functions to work on your server, these libraries must be installed:

Installation on Linux Systems

PHP 5+: Zip functions and the Zip library is not enabled by default and must be downloaded from the links above. Use the –with-zip=DIR configure option to include Zip support.

Installation on Windows Systems

PHP 5+: Zip functions is not enabled by default, so the php_zip.dll and the ZZIPlib library must be downloaded from the link above. php_zip.dll must be enabled inside of php.ini.

To enable any PHP extension, the PHP extension_dir setting (in the php.ini file) should be set to the directory where the PHP extensions are located. An example extension_dir value is c:\php\ext.


PHP Zip File Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
zip_close() Closes a ZIP file 4
zip_entry_close() Closes an entry in the ZIP file 4
zip_entry_compressedsize() Returns the compressed size of an entry in the ZIP file 4
zip_entry_compressionmethod() Returns the compression method of an entry in the ZIP file 4
zip_entry_filesize() Returns the actual file size of an entry in the ZIP file 4
zip_entry_name() Returns the name of an entry in the ZIP file 4
zip_entry_open() Opens an entry in the ZIP file for reading 4
zip_entry_read() Reads from an open entry in the ZIP file 4
zip_open() Opens a ZIP file 4
zip_read() Reads the next entry in a ZIP file 4

PHP Zip File Constants

NONE


PHP Quiz



You can test your PHP skills with W3Schools’ Quiz.


The Test

The test contains 20 questions and there is no time limit.

The test is not official, it’s just a nice way to see how much you know, or don’t know, about PHP.


Your Score Will be Counted

You will get 1 point for each correct answer. At the end of the Quiz, your total score will be displayed. Maximum score is 20 points.

Good luck! Start the PHP Quiz


W3Schools PHP Certificate



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Do you want a career with a future? You should add regular updates to your skills and knowledge. Unless, you have already decided that your current skills and job are good enough for your future.

Knowledge is power, especially in the current job market. Documentation of your skills enables you to move upwards in your organization.

Getting a certificate proves your commitment to upgrade your skills, gives you the credibility needed for more responsibilities, larger projects, and a higher salary.

In addition, documented knowledge is often the key factor when hiring new personnel. Your certificate might advance your career or help you to start a new one.

Also have in mind that employees with certifications increase their company’s chances of retaining old and getting new customers. You will do your company a favor getting certified. Expect your company to support you in this.


The HTML Developer Certificate

The HTML Developer Certificate is for developers who want to document their knowledge of HTML 4.01, XHTML, and CSS.


The JavaScript Developer Certificate

The JavaScript Developer Certificate is for developers who want to document their knowledge of JavaScript and the HTML DOM.


The XML Developer Certificate

The XML Developer Certificate is for developers who want to document their knowledge of XML, XML DOM and XSLT.


The ASP Developer Certificate

The ASP Developer Certificate is for developers who want to document their knowledge of Active Server Pages, SQL, and ADO.


The PHP Developer Certificate

The PHP Developer Certificate is for developers who want to document their knowledge of PHP and SQL (MySQL).


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Tài liệu XML

XML Basic

Introduction to XML


What you should already know

Before you continue you should have some basic understanding of the following:

  • WWW, HTML and the basics of building Web pages
  • Web scripting languages like JavaScript and VBScript

If you want to study these subjects, Go To W3Schools


What is XML?

  • XML stands for EXtensible Markup Language
  • XML is a markup language much like HTML.
  • XML was designed to describe data.
  • XML tags are not predefined in XML. You must define your own tags.
  • XML is self describing.
  • XML uses a DTD (Document Type Definition) to formally describe the data.

The main difference between XML and HTML

XML is not a replacement for HTML.
XML and HTML were designed with different goals:

XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.

HTML is about displaying information, XML is about describing information.


XML is extensible

The tags used to markup HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard.

XML allows the author to define his own tags and his own document structure.


XML is a complement to HTML

It is important to understand that XML is not a replacement for HTML. In the future development of the Web it is most likely that XML will be used to structure and describe the Web data, while HTML will be used to format and display the same data.


XML in future Web development

We have been participating in XML development since its creation. It has been amazing to see how quickly the XML standard has been developed, and how quickly a large number of software vendors have adopted the standard.

We strongly believe that XML will be as important to the future of the Web as HTML has been to the foundation of the Web. XML is the future for all data transmission and data manipulation over the Web.

How can XML be used?


  • XML can keep data separated from your HTML
  • XML can be used to store data inside HTML documents
  • XML can be used as a format to exchange information
  • XML can be used to store data in files or in databases

XML can keep data separated from your HTML

HTML pages are used to display data. Data is often stored inside HTML pages. With XML this data can now be stored in a separate XML file. This way you can concentrate on using HTML for formatting and display, and be sure that changes in the underlying data will not force changes to any of your HTML code.


XML can also store data inside HTML documents

XML data can also be stored inside HTML pages as “Data Islands”. You can still concentrate on using HTML for formatting and displaying the data. 


XML can be used to exchange data

In the real world, computer systems and databases contain data in incompatible formats. One of the most time consuming challenges for developers has been to exchange data between such systems over the Internet. Converting the data to XML can greatly reduce this complexity and create data that can be read by different types of applications.


XML can be used to store data

XML can also be used to store data in files or in databases. Applications can be written to store and retrieve information from the store, and generic applications can be used to display the data.

XML Syntax


An example XML document:

<?xml version="1.0"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

The first line in the document: The XML declaration should always be included. It defines the XML version of the document. In this case the document conforms to the 1.0 specification of XML:

<?xml version="1.0"?>

The next line defines the first element of the document (the root element):

<note>

The next lines defines 4 child elements of the root (to, from, heading, and body):

<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>

The last line defines the end of the root element:

</note>

 


All XML elements must have a closing tag

In HTML some elements do not have to have a closing tag. The following code is legal in HTML:

<p>This is a paragraph
<p>This is another paragraph

In XML all elements must have a closing tag like this:

<p>This is a paragraph</p>
<p>This is another paragraph</p> 

 


XML tags are case sensitive

XML tags are case sensitive. The tag <Letter> is different from the tag <letter>.

Opening and closing tags must therefore be written with the same case:

<Message>This is incorrect</message>

 

<message>This is correct</message>

 


All XML elements must be properly nested

In HTML some elements can be improperly nested within each other like this:

<b><i>This text is bold and italic</b></i>

In XML all elements must be properly nested within each other like this

<b><i>This text is bold and italic</i></b>

 


All XML documents must have a root tag

All XML documents must contain a single tag pair to define the root element. All other elements must be nested within the root element. All elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element:

<root>
  <child>
    <subchild>
    </subchild>
  </child>
</root>

 


Attribute values must always be quoted

XML elements can have attributes in name/value pairs just like in HTML. In XML the attribute value must always be quoted. Study the two XML documents below. The first one is incorrect, the second is correct:

<?xml version="1.0"?>
<note date=12/11/99>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

<?xml version="1.0"?>
<note date="12/11/99">
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

XML Attributes


XML Attributes

XML attributes are normally used to describe XML elements, or to provide additional information about elements. From HTML you can remember this construct: <IMG SRC=”computer.gif”>. In this HTML example SRC is an attribute to the IMG element. The SRC attribute provides additional information about the element.

Attributes are always contained within the start tag of an element. Here are some examples:

HTML examples:

<img src="computer.gif">
<a href="demo.asp">
XML examples:

<file>
<person>

Usually, or most common, attributes are used to provide information that is not a part of the content of the XML document. Did you understand that? Here is another way to express that: Often attribute data is more important to the XML parser than to the reader. Did you understand it now? Anyway, in the example above, the person id is a counter value that is irrelevant to the reader, but important to software that wants to manipulate the person element. 


Use of Elements vs. Attributes

Take a look at these examples:

Using an Attribute for sex:

<person sex="female">
  <firstname>Anna</firstname>
  <lastname>Smith</lastname>
</person>

Using an Element for sex:

<person>
  <sex>female</sex>
  <firstname>Anna</firstname>
  <lastname>Smith</lastname>
</person>

In the first example sex is an attribute. In the last example sex is an element. Both examples provides the same information to the reader.

There are no fixed rules about when to use attributes to describe data, and when to use elements. My experience is however; that attributes are handy in HTML, but in XML you should try to avoid them, as long as the same information can be expressed using elements.

Here is another example, demonstrating how elements can be used instead of attributes. The following three XML documents contain exactly the same information. A date attribute is used in the first, a date element is used in the second, and an expanded date element is used in the third:

<?xml version="1.0"?>
<note date="12/11/99">
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note> 
<?xml version="1.0"?>
<note>
<date>12/11/99</date>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note> 
<?xml version="1.0"?>
<note>
<date>
  <day>12</day>
  <month>11</month>
  <year>99</year>
</date>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

 


Avoid using attributes? (I say yes!)

Why should you avoid using attributes? Should you just take my word for it? These are some of the problems using attributes:

  • attributes can not contain multiple values (elements can)
  • attributes are not expandable (for future changes)
  • attributes can not describe structures (like child elements can)
  • attributes are more difficult to manipulate by program code
  • attribute values are not easy to test against a DTD

If you start using attributes as containers for XML data, you might end up with documents that are both difficult to maintain and to manipulate. What I’m trying to say is that you should use elements to describe your data. Use attributes only to provide information that is not relevant to the reader. Please don’t end up like this:

<?xml version="1.0"?>
<note day="12" month="11" year="99"
to="Tove" from="Jani" heading="Reminder"
body="Don't forget me this weekend!">
</note>

This don’t look much like XML. Got the point?


An Exception to my Attribute rule

Rules always have exceptions. My rule about not using attributes has one too:

Sometimes I assign ID references to elements in my XML documents. These ID references can be used to access XML element in much the same way as the NAME or ID attributes in HTML. This example demonstrates this:

<?xml version="1.0"?>
<messages>
  <note>
    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body>Don't forget me this weekend!</body>
  </note>

  <note>
    <to>Jani</to>
    <from>Tove</from>
    <heading>Re: Reminder</heading>
    <body>I will not!</body>
  </note> 
</messages>

The ID in these examples is just a counter, or a unique identifier, to identify the different notes in the XML file.

XML Validation


“Well Formed” XML documents

A “Well Formed” XML document is a document that conforms to the XML syntax rules that we described in the previous chapter.

The following is a “Well Formed” XML document:

<?xml version="1.0"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

 


“Valid” XML documents

A “Valid” XML document is a “Well Formed” XML document which conforms to the rules of a Document Type Definition (DTD).

The following is the same document as above but with an added reference to a DTD:

<?xml version="1.0"?>
<!DOCTYPE note SYSTEM "InternalNote.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

 


More about XML DTD

You can read more about DTD in the chapter XML DTD.

XML in Netscape and in Explorer


XML in this Web

Many applications support XML in a number of ways. In this Web we focus on the XML support in Internet Explorer 5.0. Some visitors have complained about this, but we don’t do it because IE5 is the only performer in the XML field. We do it because it is the only practical way to demonstrate XML to a large audience over the Web.

So – while we are waiting for Netscape – most of our software examples will work only with IE5. If you want to learn XML the easy way – with lots of examples for you to try out – you will have to live with that.


XML in Netscape Navigator 5

Netscape has promised full XML support in its new Navigator 5 browser. We hope that this will include standard support for the W3C XML, just as it does in Internet Explorer 5.

Based on previous experience we can only hope that Navigator and Explorer will be fully compatible in the future XML field.

Your option at the moment – if you want to work with Netscape and XML – is to work with XML on your server and transform your XML to HTML before it is sent to the browser. You can read more about  transforming XML to HTML in the chapters about XSL.


XML in Internet Explorer 5

Internet Explorer 5 fully supports the international standards for both XML 1.0 and the XML Document Object Model (DOM). These standards are set by the World Wide Web Consortium (W3C).

You can download IE5 from http://www.microsoft.com/windows/ie/

Internet Explorer 5.0 has the following XML support:

  • Viewing of XML documents
  • Full support for W3C DTD standards
  • XML embedded in HTML as Data Islands
  • Binding XML data to HTML elements
  • Formatting XML with XSL
  • Formatting XML with CSS
  • Support for CSS Behaviors
  • Access to the XML DOM

Examples of these features are given in the next chapters.

Viewing XML files with IE5


Viewing XML with Internet Explorer 5

You can use IE5 to view an XML document just as you view any HTML page. There are several ways to open an XML document. You can click on a link, type the URL into the address bar, double-click on an XML document in a folder, and so on.

If you point IE5 to an XML document, IE5 will display the document with its root element and child elements expanded. A plus (+) or minus sign (-) to the left of the XML elements can be clicked to expand or collapse the element structure, and if you only want to view the raw XML source, you can select “View Source” from the browser menu.

If you click on the following filename: note.xml, IE5 will open the file in an explorer like view.


Viewing an invalid XML file

If an erroneous XML file is opened with IE5, IE5 will report the error in the file.

If you click on the following filename: note_error.xml, IE5 will display an error message.


Other examples

To help you get the feeling of different types of XML data, we have collected the following XML data files for you:

An XML CD catalog

An XML plant catalog

A Simple Menu

Displaying XML


Displaying XML with JavaScript

To display XML data inside an HTML page you can use JavaScript to import data from an XML file. To see how XML and HTML complement each other this way; first look at the XML document (note.xml), then open the HTML document (note.htm) that contains a JavaScript which reads an XML file and displays the information inside the HTML page.

To see how it works, Try It Yourself 


Displaying XML with CSS

To demonstrate how XML files can be formatted with CSS we have compiled the following XML files: 

Take a look at this pure XML file: The CD Catalog
Then look at this style sheet: The CSS file
Finally, view: The CD Catalog formatted with the CSS file

Even if it looks right to use CSS this way, we strongly believe that formatting with XSL will be the standard way to format XML in future (or as soon as the main browsers support it).


Writing your Homepage in XML?

Will we write our homepages in XML in the future?

No, we don’t think so. But we could not resist giving it a try : A homepage written in XML

This might be the answer: Take a XHTML tutorial


Displaying XML with XSL

Follow this link to see how the content of an XML file can be displayed in the browser.

Follow this link to see how the same XML file is displayed by using an XSL style sheet.

Follow this link to see how the same data can be prepared by the server and returned to the browser as an HTML file.


To learn more about XSL

To learn more about XSL go to the XSL chapter.

XML_DTD

Introduction to DTD


The purpose of a DTD is to define the legal building blocks of an XML document. It defines the document structure with a list of legal elements. A DTD can be declared inline in your XML document, or as an external reference.


Internal DTD

This is an XML document with a Document Type Definition: (Open it in IE5, and select view source)

<?xml version="1.0"?>
<!DOCTYPE note [
  <!ELEMENT note    (to,from,heading,body)>
  <!ELEMENT to      (#PCDATA)>
  <!ELEMENT from    (#PCDATA)>
  <!ELEMENT heading (#PCDATA)>
  <!ELEMENT body    (#PCDATA)>
]>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

The DTD is interpreted like this:
!ELEMENT note (in line 2) defines the element “note” as having four elements: “to,from,heading,body”.
!ELEMENT to (in line 3) defines the “to” element  to be of the type “CDATA”.
!ELEMENT from (in line 4) defines the “from” element to be of the type “CDATA”
and so on…..


External DTD

This is the same XML document with an external DTD:  (Open it in IE5, and select view source)

<?xml version="1.0"?>
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

This is a copy of the file “note.dtd” containing the Document Type Definition:

<?xml version="1.0"?>
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>

 


Why use a DTD?

XML provides an application independent way of sharing data. With a DTD, independent groups of people can agree to use a common DTD for interchanging data. Your application can use a standard DTD to verify that data that you receive from the outside world is valid. You can also use a DTD to verify your own data.

A lot of forums are emerging to define standard DTDs for almost everything in the areas of data exchange. Take a look at: CommerceNet’s XML exchange and http://www.schema.net.

DTD – XML building blocks


The building blocks of XML documents

XML documents (and HTML documents) are made up by the following building blocks:

Elements, Tags, Attributes, Entities, PCDATA, and CDATA

This is a brief explanation of each of the building blocks:


Elements

Elements are the main building blocks of both XML and HTML documents.

Examples of HTML elements are “body” and “table”. Examples of XML elements could be “note” and “message”. Elements can contain text, other elements, or be empty. Examples of empty HTML elements are “hr”, “br” and “img”.


Tags

Tags are used to markup elements.

A starting tag like <element_name> mark up the beginning of an element, and an ending tag like </element_name>  mark up the end of  an element.

Examples:
A body element: <body>body text in between</body>.
A message element: <message>some message in between</message>


Attributes

Attributes provide extra information about elements.

Attributes are placed inside the start tag of an element. Attributes come in name/value pairs. The following “img” element has an additional information about a source file:

<img src="computer.gif" />

The name of the element is “img”. The name of the attribute is “src”. The value of the attribute is “computer.gif”. Since the element itself is empty it is closed by a ” /”.


PCDATA

PCDATA means parsed character data.

Think of character data as the text found between the start tag and the end tag of an XML element.

PCDATA is text that will be parsed by a parser. Tags inside the text will be treated as markup and entities will be expanded. 


CDATA

CDATA also means character data.

CDATA is text that will NOT be parsed by a parser. Tags inside the text will NOT be treated as markup and entities will not be expanded.


Entities

Entities as variables used to define common text. Entity references are references to entities.

Most of you will known the HTML entity reference: “&nbsp;”  that is used to insert an extra space in an HTML document. Entities are expanded when a document is parsed by an XML parser.

The following entities are predefined in XML:

Entity References Character
&lt;
&gt;
&amp; &
&quot;
&apos;

  DTD – Elements


Declaring an Element

In the DTD, XML elements are declared with an element declaration. An element declaration has the following syntax:

<!ELEMENT element-name (element-content)>

 


Empty elements

Empty elements are declared with the keyword EMPTY inside the parentheses:

<!ELEMENT element-name (EMPTY)>

example:
<!ELEMENT img (EMPTY)>

 


Elements with data

Elements with data are declared with the data type inside parentheses:

<!ELEMENT element-name (#CDATA)>
or
<!ELEMENT element-name (#PCDATA)>
or
<!ELEMENT element-name (ANY)>
example:
<!ELEMENT note (#PCDATA)>

#CDATA means the element contains character data that is not supposed to be parsed by a parser.
#PCDATA means that the element contains data that IS going to be parsed by a parser.
The keyword ANY declares an element with any content.

If a #PCDATA section contains elements, these elements must also be declared.


Elements with children (sequences)

Elements with one or more children are defined with the name of the children elements inside the parentheses:

<!ELEMENT element-name (child-element-name)>
or
<!ELEMENT element-name (child-element-name,child-element-name,.....)>
example:
<!ELEMENT note (to,from,heading,body)>

When children are declared in a sequence separated by commas, the children must appear in the same sequence in the document. In a full declaration, the children must also be declared, and the children can also have children. The full declaration of the note document will be:

<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to      (#CDATA)>
<!ELEMENT from    (#CDATA)>
<!ELEMENT heading (#CDATA)>
<!ELEMENT body    (#CDATA)>

 


Wrapping

If the DTD is to be included in your XML source file, it should be wrapped in a DOCTYPE definition with the following syntax:

<!DOCTYPE root-element [element-declarations]>
example: 
<?xml version="1.0"?>
<!DOCTYPE note [
  <!ELEMENT note (to,from,heading,body)>
  <!ELEMENT to      (#CDATA)>
  <!ELEMENT from    (#CDATA)>
  <!ELEMENT heading (#CDATA)>
  <!ELEMENT body    (#CDATA)>
]>
<note>
  <to>Tove</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>Don't forget me this weekend</body>
</note>

 


Declaring only one occurrence of the same element 

<!ELEMENT element-name (child-name)>
example
<!ELEMENT note (message)>

The example declaration above declares that the child element message can only occur one time inside the note element.


Declaring minimum one occurrence of the same element

<!ELEMENT element-name (child-name+)>
example
<!ELEMENT note (message+)>

The + sign in the example above declares that the child element message must occur one or more times inside the note element.


Declaring zero or more occurrences of the same element 

<!ELEMENT element-name (child-name*)>
example
<!ELEMENT note (message*)>

The * sign in the example above declares that the child element message can occur zero or more times inside the note element.


Declaring zero or one occurrences of the same element 

<!ELEMENT element-name (child-name?)>
example
<!ELEMENT note (message?)>

The ? sign in the example above declares that the child element message can occur zero or one times inside the note element.


Declaring mixed content

example
<!ELEMENT note (to+,from,header,message*,#PCDATA)>

The example above declares that the element note must contain at least one to child element, exactly one from child element, exactly one header, zero or more message, and some other parsed character data as well. Puh!

DTD – Attributes


Declaring Attributes

In the DTD, XML element attributes are declared with an ATTLIST declaration. An attribute declaration has the following syntax:

<!ATTLIST element-name attribute-name attribute-type default-value>

As you can see from the syntax above, the ATTLIST declaration defines the element which can have the attribute, the name of the attribute, the type of the attribute, and the default attribute value.

The attribute-type can have the following values:

Value Explanation
CDATA
The value is character data
(eval|eval|..)
The value must be an enumerated value
ID
The value is an unique id
IDREF
The value is the id of another element
IDREFS
The value is a list of other ids
NMTOKEN
The value is a valid XML name
NMTOKENS
The value is a list of valid XML names
ENTITY
The value is an entity
ENTITIES
The value is a list of entities
NOTATION
The value is a name of a notation
xml:
The value is predefined

The attribute-default-value can have the following values:

Value Explanation
#DEFAULT value
The attribute has a default value
#REQUIRED
The attribute value must be included in the element
#IMPLIED
The attribute does not have to be included
#FIXED value
The attribute value is fixed

 


Attribute declaration example

DTD example:
<!ELEMENT square EMPTY>
  <!ATTLIST square width CDATA "0">

XML example:
<square width="100"></square>

In the above example the element square is defined to be an empty element with the attributes width of  type CDATA. The width attribute has a default value of 0. 


Default attribute value

Syntax:
<!ATTLIST element-name attribute-name CDATA "default-value">

DTD example:
<!ATTLIST payment type CDATA "check">

XML example:
<payment>

Specifying a default value for an attribute, assures that the attribute will get a value even if the author of the XML document didn’t include it.


Implied attribute

Syntax:
<!ATTLIST element-name attribute-name attribute-type #IMPLIED>
DTD example:
<!ATTLIST contact fax CDATA #IMPLIED>

XML example:
<contact fax="555-667788">

Use an implied attribute if you don’t want to force the author to include an attribute and you don’t have an option for a default value either. 


Required attribute

Syntax:
<!ATTLIST element-name attribute_name attribute-type #REQUIRED>
DTD example:
<!ATTLIST person number CDATA #REQUIRED>

XML example:
<person number="5677">

Use a required attribute if you don’t have an option for a default value, but still want to force the attribute to be present.


Fixed attribute value

Syntax:
<!ATTLIST element-name attribute-name attribute-type #FIXED "value">
DTD example:
<!ATTLIST sender company CDATA #FIXED "Microsoft">

XML example:
<sender company="Microsoft">

Use a fixed attribute value when you want an attribute to have a fixed value without allowing the author to change it. If an author includes another value, the XML parser will return an error.


Enumerated attribute values

Syntax:
<!ATTLIST element-name attribute-name (eval|eval|..) default-value>
DTD example:
<!ATTLIST payment type (check|cash) "cash">

XML example:
<payment>
or
<payment>

Use enumerated attribute values when you want the attribute values to be one of a fixed set of legal values.

DTD – Entities


Entities

  • Entities as variables used to define shortcuts to common text.
  • Entity references are references to entities.
  • Entities can be declared internal.
  • Entities can be declared external

Internal Entity Declaration

Syntax: 
<!ENTITY entity-name "entity-value">

DTD Example:
<!ENTITY writer "Jan Egil Refsnes.">
<!ENTITY copyright "Copyright XML101.">
XML example:
<author>&writer;&copyright;</author>

 


External Entity Declaration

Syntax: 
<!ENTITY entity-name SYSTEM "URI/URL">

DTD Example:
<!ENTITY writer    SYSTEM "http://www.xml101.com/entities/entities.xml">
<!ENTITY copyright SYSTEM "http://www.xml101.com/entities/entities.dtd">
XML example:
<author>&writer;&copyright;</author>

DTD Validation


Validating with the XML Parser

If you try to open an XML document, the XML Parser might generate an error. By accessing the parseError object, the exact error code, the error text, and even the line that caused the error can be retrieved:

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.validateOnParse="true"
xmlDoc.load("note_dtd_error.xml")

document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)

Try it Yourself or or just look at the XML file


Turning Validation off

Validation can be turned off by setting the XML parser’s validateOnParse=”false”.

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.validateOnParse="false"
xmlDoc.load("note_dtd_error.xml")

document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)

The parseError Object

You can read more about the parseError object in the Dom section of this Web.

DTD – Examples from the Net


TV Scedule DTD

By David Moisan. Copied from his Web: http://www1.shore.net/~dmoisan/ 

<!DOCTYPE TVSCHEDULE [ 

<!ELEMENT TVSCHEDULE (CHANNEL+)>
<!ELEMENT CHANNEL (BANNER, DAY+)>
<!ELEMENT BANNER (#PCDATA)>
<!ELEMENT DAY ((DATE, HOLIDAY) | (DATE, PROGRAMSLOT+))+>
<!ELEMENT HOLIDAY (#PCDATA)>
<!ELEMENT DATE (#PCDATA)>
<!ELEMENT PROGRAMSLOT (TIME, TITLE, DESCRIPTION?)>
<!ELEMENT TIME (#PCDATA)>
<!ELEMENT TITLE (#PCDATA)> 
<!ELEMENT DESCRIPTION (#PCDATA)>

<!ATTLIST TVSCHEDULE NAME CDATA #REQUIRED>
<!ATTLIST CHANNEL CHAN CDATA #REQUIRED>
<!ATTLIST PROGRAMSLOT VTR CDATA #IMPLIED>
<!ATTLIST TITLE RATING CDATA #IMPLIED>
<!ATTLIST TITLE LANGUAGE CDATA #IMPLIED>

]>

 


A Report DTD

By Richard Erlander. Copied from his Web: http://pdbeam.uwaterloo.ca/~rlander/ 

<!DOCTYPE REPORT [ 

<!ELEMENT REPORT (TITLE,(SECTION|SHORTSECT)+)>
<!ELEMENT SECTION (TITLE,%BODY;,SUBSECTION*)>
<!ELEMENT SUBSECTION (TITLE,%BODY;,SUBSECTION*)>
<!ELEMENT SHORTSECT (TITLE,%BODY;)>
<!ELEMENT TITLE %TEXT;>
<!ELEMENT PARA %TEXT;>
<!ELEMENT LIST (ITEM)+>
<!ELEMENT ITEM (%BLOCK;)>
<!ELEMENT CODE (#PCDATA)>
<!ELEMENT KEYWORD (#PCDATA)>
<!ELEMENT EXAMPLE (TITLE?,%BLOCK;)>
<!ELEMENT GRAPHIC EMPTY>

<!ATTLIST REPORT security (high | medium | low ) "low">
<!ATTLIST CODE type CDATA #IMPLIED>
<!ATTLIST GRAPHIC file ENTITY #REQUIRED>

<!ENTITY xml "Extensible Markup Language">
<!ENTITY sgml "Standard Generalized Markup Language">
<!ENTITY pxa "Professional XML Authoring">
<!ENTITY % TEXT "(#PCDATA|CODE|KEYWORD|QUOTATION)*">
<!ENTITY % BLOCK "(PARA|LIST)+">
<!ENTITY % BODY "(%BLOCK;|EXAMPLE|NOTE)+">

<!NOTATION GIF SYSTEM "">
<!NOTATION JPG SYSTEM "">
<!NOTATION BMP SYSTEM "">

]>

 


Newspaper Article DTD

Copied from http://www.vervet.com/ 

<!DOCTYPE NEWSPAPER [ 

<!ELEMENT NEWSPAPER (ARTICLE+)>
<!ELEMENT ARTICLE (HEADLINE, BYLINE, LEAD, BODY, NOTES)>
<!ELEMENT HEADLINE (#PCDATA)>
<!ELEMENT BYLINE (#PCDATA)>
<!ELEMENT LEAD (#PCDATA)>
<!ELEMENT BODY (#PCDATA)>
<!ELEMENT NOTES (#PCDATA)> 

<!ATTLIST ARTICLE AUTHOR CDATA #REQUIRED>
<!ATTLIST ARTICLE EDITOR CDATA #IMPLIED>
<!ATTLIST ARTICLE DATE CDATA #IMPLIED>
<!ATTLIST ARTICLE EDITION CDATA #IMPLIED>

<!ENTITY NEWSPAPER "Vervet Logic Times">
<!ENTITY PUBLISHER "Vervet Logic Press">
<!ENTITY COPYRIGHT "Copyright 1998 Vervet Logic Press">

]>

 


Product Catalog DTD

Copied from http://www.vervet.com/ 

<!DOCTYPE CATALOG [ 

<!ELEMENT CATALOG (PRODUCT+)>
<!ELEMENT PRODUCT (SPECIFICATIONS+, OPTIONS?, PRICE+, NOTES?)>
<!ELEMENT SPECIFICATIONS (#PCDATA)>
<!ELEMENT OPTIONS (#PCDATA)>
<!ELEMENT PRICE (#PCDATA)>
<!ELEMENT NOTES (#PCDATA)>

<!ATTLIST PRODUCT NAME CDATA #IMPLIED>
<!ATTLIST CATEGORY (HandTool | Table | Shop-Professional) "HandTool">
<!ATTLIST PARTNUM CDATA #IMPLIED>
<!ATTLIST PLANT (Pittsburgh | Milwaukee | Chicago) "Chicago">
<!ATTLIST INVENTORY (InStock | Backordered | Discontinued) "InStock">
<!ATTLIST SPECIFICATIONS WEIGHT CDATA #IMPLIED>
<!ATTLIST POWER CDATA #IMPLIED>
<!ATTLIST OPTIONS FINISH (Metal | Polished | Matte) "Matte">
<!ATTLIST OPTIONS ADAPTER (Included | Optional | NotApplicable) "Included">
<!ATTLIST OPTIONS CASE (HardShell | Soft | NotApplicable) "HardShell">
<!ATTLIST PRICE MSRP CDATA #IMPLIED>
<!ATTLIST PRICE WHOLESALE CDATA #IMPLIED>
<!ATTLIST PRICE STREET CDATA #IMPLIED>
<!ATTLIST PRICE SHIPPING CDATA #IMPLIED>

<!ENTITY AUTHOR "John Doe">
<!ENTITY COMPANY "JD Power Tools, Inc.">
<!ENTITY EMAIL "jd@jd-tools.com">

]>

XML_DOM

The XML DOM


The Document Object Model

The DOM is a programming interface for HTML and XML documents. It defines the way a document can be accessed and manipulated. 

Using a DOM, a programmer can create a document, navigate its structure, and add, modify, or delete its elements.

As a W3C specification, one important objective for the DOM has been to provide a standard programming interface that can be used in a wide variety of environments and applications.

The W3C DOM has been designed to be used with any programming language.


The Node Interface

As you will se in the next section, a program called an XML parser can be used to load an XML document into the memory of your computer. When the document is loaded, it’s information can be retrieved and manipulated by accessing the Document Object Model (DOM).

The DOM represents a tree view of the XML document. The documentElement is the top-level of the tree. This element has one or many childNodes that represent the branches of the tree.

A Node Interface is used to read and write (or access if you like) the individual elements in the XML node tree. The childNodes property of the documentElement can be accesses with a for/each construct to enumerate each individual node.

The Microsoft XML parser used to demonstrate the DOM in this Web, supports all the necessary functions to traverse the node tree, access the nodes and their attribute values, insert and delete nodes, and convert the node tree back to XML.

All the demonstrated Microsoft XML parser functions are from the official W3C XML DOM recommendation, apart from the load and loadXML functions. (Believe it or not: The official DOM does not include standard functions for loading XML documents !!)

A total of 13 node types are currently supported by the Microsoft XML parser. The following table lists the most commonly used node types:

Node Type Example
Document type <!DOCTYPE food SYSTEM “food.dtd”>
Processing instruction <?xml version=”1.0″?>
Element <drink type=”beer”>Carlsberg</drink>
Attribute type=”beer”
Text Carlsberg

To view the examples in this Web, you have to use Microsoft Internet Explorer 5.0 !

Parsing the DOM


Using the XML parser

To read and update – create and manipulate – an XML document, you need an XML parser. The Microsoft XML parser is a COM component that comes with Microsoft Internet Explorer 5.0. Once you have installed IE 5.0, the parser is available to scripts inside HTML documents and ASP files.

The Microsoft XMLDOM parser features a language-neutral programming model that:

  • Supports JavaScript, VBScript, Perl, VB, Java, C++ and more
  • Supports W3C XML 1.0 and XML DOM
  • Supports DTD and validation

If you are using JavaScript in IE 5.0, you can create an XML document object with the following code:

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")

If you are using VBScript you create the XML document object with the following code:

set xmlDoc = CreateObject("Microsoft.XMLDOM")

If you are using VBScript in an Active Server Page (ASP), you can use the following code:

set xmlDoc = Server.CreateObject("Microsoft.XMLDOM")

Loading an XML file into the parser

The following code loads an existing XML document (note.xml) into the XML parser:

<script>
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("note.xml")
// ....... processing the document goes here
</script>

The first line of the script creates an instance of the Microsoft XML parser. The third line tells the parser to load an XML document called note.xml. The second line assures that the parser will halt execution until the document is fully loaded.

JUST TRY IT


Loading pure XML text into the parser

The following code loads a text string into the XML parser:

<script>

var text="<note>"
text=text+"<to>Tove</to><from>Jani</from>"
text=text+"<heading>Reminder</heading>"
text=text+"<body>Don't forget me this weekend!</body>"
text=text+"</note>"

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.loadXML(text)
// ....... processing the document goes here
</script>

Note that the “loadXML” method (instead of the “load” method) is used to load a text string.

Parser Errors


The parseError Object

If you try to open an XML document, the XML Parser might generate an error. By accessing the parseError object, the exact error code, the error text, and even the line that caused the error can be retrieved:


File Error

In this example we let the XML parser try to load a non existing file, and display some of its error properties:

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("ksdjf.xml")

document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)

XML Error

Now we let the parser load an XML document that is not well formed. (if you don’t know what well formed XML is, read the XML part of this Web)

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("note_error.xml")

document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)

Try it Yourself or just look at the XML file


The parseError Properties

Property             Description

errorCode            Returns a long integer error code

reason                 Returns a string explaining the reason for the error

line                       Returns a long integer representing the line number for the error

linePos                Returns a long integer representing the line position for the error

srcText                 Returns a string containing the line that caused the error

url                         Returns the url pointing the loaded document

filePos                 Returns a long integer file position of the error

Accessing the DOM


Traversing the node tree

One very common way to extract XML elements from an XML document is to traverse the node three and extract the text value of each elements. A small snippet of programming code like a VBScript for/each construct can be written to demonstrate this.

The following VBScript code traverses an XML node tree, and displays the XML elements in the browser:

set xmlDoc=CreateObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("note.xml")

for each x in xmlDoc.documentElement.childNodes
  document.write(x.nodename)
  document.write(": ")
  document.write(x.text)
next

JUST TRY IT and also try to traverse our CD catalog example.


Providing HTML content from XML files

One of the great promises of XML is the possibility to separate HTML documents from their data. By using an XML parser inside the browser, an HTML page can be constructed as a static document, with an embedded JavaScript to provide dynamic data. When you add that these JavaScripts can access Active Server Pages from a Web server, the future looks very bright.

The following JavaScript reads XML data from an XML document and writes the XML data into (waiting) HTML elements.

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("note.xml")

nodes = xmlDoc.documentElement.childNodes

to.innerText = nodes.item(0).text
from.innerText = nodes.item(1).text
header.innerText = nodes.item(2).text
body.innerText = nodes.item(3).text

JUST TRY IT


Accessing XML elements by name

The following JavaScript reads XML data from an XML document and writes the XML data into (waiting) HTML elements.

var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load("note.xml")

document.write(xmlDoc.getElementsByTagName("from").item(0).text)

XML_XSL

Introduction to XSL

by Jan Egil Refsnes


XSL – The Style Sheet of XML?

HTML pages uses predefined tags, and the meaning of these tags is well understood: <p> means a paragraph and <h1> means a header, and the browser knows how to display these pages.

With XML we can use any tags we want, and the meaning of these tags are not automatically understood by the browser: <table> could mean a HTML table or maybe a piece of furniture. Because of the nature of XML, there is no standard way to display an XML document.

In order to display XML documents, it is necessary to have a mechanism to describe how the document should be displayed. One of these mechanisms is Cascading Style Sheets (CSS), but XSL (eXtensible Stylesheet Language) is the preferred style sheet language of XML, and XSL is far more sophisticated than the CSS  used by HTML.


XSL – More than a Style Sheet

XSL consists of two parts:

  • a method for transforming XML documents
  • a method for formatting XML documents

If you don’t understand the meaning of this, think of XSL as a language that can transform XML into HTML, a language that can filter and sort XML data and a language that can format XML data, based on the data value, like displaying negative numbers in red. 


XSL – What can it do?

XSL can be used to define how an XML file should be displayed by transforming the XML file into a format that is recognizable to a browser. One such format is HTML. Normally XSL does this by transforming each XML element into an HTML element.

XSL can also add completely new elements into the output file, or remove elements. It can rearrange and sort the elements, test and make decisions about which elements to display, and a lot more.


A note about XSL in IE5

XSL in Internet Explorer 5.0 is not 100% compatible with the latest released W3C XSL standard. That is because IE 5 was released before the standard was completely settled. Microsoft has promised to solve this problem in the 5.5 release.

XSL – Transformation


Transforming XML to HTML

What if you want to transform the following XML document (open it with IE5) into HTML?

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

Consider the following XSL document (open it with IE5) as an HTML template to populate a HTML document with XML data:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD">
      <tr>
        <td><xsl:value-of select="TITLE"/></td>
        <td><xsl:value-of select="ARTIST"/></td>
      </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

In the above file, the xsl:for-each element locates elements in the XML document and repeats a template for each one. The select attribute describes the element in the source document. The syntax for this attribute is called an XSL Pattern, and works like navigating a file system where a forward slash (/) selects subdirectories. The xsl:value-of element selects a child in the hierarchy and inserts the content of that child into the template.

Since an XSL style sheet is an XML file itself, the file begins with an xml declaration. The xsl:stylesheet element indicates that this document is a style sheet. The template has also been wrapped with xsl:template match=”/” to indicate that this is a template that corresponds to the root (/) of the XML source document.

If you add a reference to the above stylesheet to your original XML document (look at line 2), your browser will nicely transform your XML document into HTML (open it in IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<?xml-stylesheet href="cd_catalog.xsl"?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

XSL – On the Client


A JavaScript Solution

In the previous chapter I explained how XSL can be used to transform a document from XML to HTML. The trick was to add an XSL stylesheet information to the XML file, and to let the browser do the transformation.

Even if this works fine, it is not always desirable to include a stylesheet reference in the XML file, and the solution will not work in a non XML aware browser.

A much more versatile solution would be to use a JavaScript to do the XML to HTML transformation.

By using a JavaScript we are more open for these possibilities:

  • Allowing the JavaScript to do browser specific testing
  • Using different style sheets according to browser and/or user needs

That’s the beauty of XSL. One of the design goals for XSL was to make it possible to transform data from one format to another, supporting different browsers and different user needs.

XSL transformation on the client side is bound to be a major part of the browsers work tasks in the future, as we will se a growth in the specialized browser marked (think: Braille, Speaking Web, Web Printers, Handheld PCs, Mobile Phones …..).


The XML file and the XSL file

Take a new look at the XML document that you saw in the previous chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

And at the companying XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD">
      <tr>
        <td><xsl:value-of select="TITLE"/></td>
        <td><xsl:value-of select="ARTIST"/></td>
      </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

The syntax of the above XSL document was explained in the previous chapter, so it will not be explained here. But be sure to notice that the XML file does not have a reference to the XSL file, and the XSL file does not have a reference to the XML file.

IMPORTANT: The above sentence indicates that an XML file could be transformed using many different XSL files.


Transforming XML to HTML on the client

Here is the simple source code needed transform the XML file to HTML on the client (try it yourself):

<html>
<body>
<script>
// Load XML 
var xml = new ActiveXObject("Microsoft.XMLDOM")
xml.async = false
xml.load("cd_catalog.xml")

// Load the XSL
var xsl = new ActiveXObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load("cd_catalog.xsl")

// Transform
document.write(xml.transformNode(xsl))
</script>

</body>
</html>

(The example above uses JavaScript. If you don’t know to write JavaScript, you should take a trip to JavaScript School.)

The first block of code creates an instance of the Microsoft XML parser (XMLDOM), and loads the XML document into memory. The second block of code creates another instance of the parser and loads the XSL document into memory. The last line of code transforms the XML document using the XSL document, and writes the result to the HTML document.

Nice and simple.

XSL – On the Server


A Cross Browser Solution

In the previous chapter I explained how XSL can be used to transform a document from XML to HTML in the browser. The trick was to let the JavaScript use an XML parser to do the transformation.

This solution will not work with a browser that don’t support an XML parser.

To make our XML data available to all kinds of browsers, we have to transform the XML document on the SERVER and send it as pure HTML to the BROWSER.

That’s another the beauty of XSL. One of the design goals for XSL was to make it possible to transform data from one format to another on a server, returning readable data to all kinds of future browsers.

XSL transformation on the server is bound to be a major part of the Internet Information Server work tasks in the future, as we will se a growth in the specialized browser marked (think: Braille, Speaking Web, Web Printers, Handheld PCs, Mobile Phones …..).


The XML file and the XSL file

Take a new look at the XML document that you saw in the previous chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

And at the companying XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD">
      <tr>
        <td><xsl:value-of select="TITLE"/></td>
        <td><xsl:value-of select="ARTIST"/></td>
      </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

The syntax of the above XSL document was explained in the previous chapter, so it will not be explained here. But be sure to notice that the XML file does not have a reference to the XSL file, and the XSL file does not have a reference to the XML file.

IMPORTANT: The above sentence indicates that an XML file on the server could be transformed using many different XSL files.


Transforming XML to HTML on the Server

Here is the simple source code needed transform the XML file to HTML on the server (View it in your browser):

<%
'Load the XML
set xml = Server.CreateObject("Microsoft.XMLDOM")
xml.async = false
xml.load(Server.MapPath("cd_catalog.xml"))

'Load the XSL
set xsl = Server.CreateObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load(Server.MapPath("cd_catalog.xsl"))

Response.Write(xml.transformNode(xsl))
%>

(The example is an ASP file, and the code is a VBScript. If you don’t know ASP or VBScript you should take a trip to ASP School.)

The first block of code creates an instance of the Microsoft XML parser (XMLDOM), and loads the XML file into memory. The second block of code creates another instance of the parser and loads the XSL document into memory. The last line of code transforms the XML document using the XSL document, and returns the result to the browser.

Nice and simple.

XSL Sort


Where to put the Sort Information

Take a new look at the XML document that you have seen in almost every chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

To output this XML file as an ordinary HTML file, and sort it at the same time, simply add an order-by attribute to your for-each element like this:

<xsl:for-each select=”CATALOG/CD” order-by=”+ ARTIST”>

The order-by attributes takes a plus (+) or minus (-) sign, to define an ascending or descending sort order, and an element name to define the sort element.

Now take a look at your slightly adjusted XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD" order-by="+ ARTIST">
      <tr>
        <td><xsl:value-of select="TITLE"/></td>
        <td><xsl:value-of select="ARTIST"/></td>
      </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

 


Transforming it on the Client

Here is the simple source code needed transform the XML file to HTML on the client (try it yourself):

<html>
<body>
<script>
// Load XML 
var xml = new ActiveXObject("Microsoft.XMLDOM")
xml.async = false
xml.load("cd_catalog.xml")

// Load the XSL
var xsl = new ActiveXObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load("cd_catalog_sort.xsl")

// Transform
document.write(xml.transformNode(xsl))
</script>

</body>
</html>

XSL Filter Query


Where to put the Filter Information

Take a new look at the XML document that you have seen in almost every chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

To filter the XML file, simply add filter to the select attribute in your for-each element like this:

<xsl:for-each select=”CATALOG/CD[ARTIST='Bob Dylan']“>

Leagal filter operators are:

  • =  (equal)
  • =! (not equal)
  • &LT& less than
  • &GT& greater than

Now take a look at your slightly adjusted XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD[ARTIST='Bob Dylan']">
      <tr>
        <td><xsl:value-of select="TITLE"/></td>
        <td><xsl:value-of select="ARTIST"/></td>
      </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

 


Transforming it on the Client

Here is the simple source code needed transform the XML file to HTML on the client (try it yourself):

<html>
<body>
<script>
// Load XML 
var xml = new ActiveXObject("Microsoft.XMLDOM")
xml.async = false
xml.load("cd_catalog.xml")

// Load the XSL
var xsl = new ActiveXObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load("cd_catalog_filter.xsl")

// Transform
document.write(xml.transformNode(xsl))
</script>

</body>
</html>

XSL Conditional If


Where to put the IF condition

Take a new look at the XML document that you have seen in almost every chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

To put an conditional if test against the content of the file, simply add an xsl:if element to your XSL document like this:

<xsl:if match=”.[ARTIST='Bob Dylan']“>
… some output …
</xsl:if>

Now take a look at your slightly adjusted XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD">
               <xsl:if match=".[ARTIST='Bob Dylan']">
                 <tr>
          <td><xsl:value-of select="TITLE"/></td>
          <td><xsl:value-of select="ARTIST"/></td>
                 </tr>
        </xsl:if>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

 


Transforming it on the Client

Here is the simple source code needed transform the XML file to HTML on the client (try it yourself):

<html>
<body>
<script>
// Load XML 
var xml = new ActiveXObject("Microsoft.XMLDOM")
xml.async = false
xml.load("cd_catalog.xml")

// Load the XSL
var xsl = new ActiveXObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load("cd_catalog_filter.xsl")

// Transform
document.write(xml.transformNode(xsl))
</script>

</body>
</html>

XSL Conditional Coose


Where to put the Choose Condition

Take a new look at the XML document that you have seen in almost every chapter (or open it with IE5):

<?xml version="1.0" encoding="ISO8859-1" ?>
<CATALOG>
  <CD>
    <TITLE>Empire Burlesque</TITLE>
    <ARTIST>Bob Dylan</ARTIST>
    <COUNTRY>USA</COUNTRY>
    <COMPANY>Columbia</COMPANY>
    <PRICE>10.90</PRICE>
    <YEAR>1985</YEAR>
  </CD>

To insert an conditional choose test against the content of the file, simply add an xsl:choose, xsl:when and xsl:otherwise elements to your XSL document like this:

<xsl:choose>
   <xsl:when match=”.[ARTIST='Bob Dylan']“>
      … some code …
   </xsl:when>
   <xsl:otherwise>
      … some code ….
   </xsl:otherwise>
</xsl:choose>

Now take a look at your slightly adjusted XSL stylesheet (or open it with IE5):

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template match="/">
  <html>
  <body>
    <table border="2" bgcolor="yellow">
      <tr>
        <th>Title</th>
        <th>Artist</th>
      </tr>
      <xsl:for-each select="CATALOG/CD">
               <tr>
        <td><xsl:value-of select="TITLE"/></td>
               <xsl:choose>
          <xsl:when match=".[ARTIST='Bob Dylan']">
            <td bgcolor="#ff0000"><xsl:value-of select="ARTIST"/></td>
          </xsl:when>
          <xsl:otherwise>
            <td><xsl:value-of select="ARTIST"/></td>
          </xsl:otherwise>
        </xsl:choose>
               </tr>
      </xsl:for-each>
    </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

 


Transforming it on the Client

Here is the simple source code needed transform the XML file to HTML on the client (try it yourself):

<html>
<body>
<script>
// Load XML 
var xml = new ActiveXObject("Microsoft.XMLDOM")
xml.async = false
xml.load("cd_catalog.xml")

// Load the XSL
var xsl = new ActiveXObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load("cd_catalog_filter.xsl")

// Transform
document.write(xml.transformNode(xsl))
</script>

</body>
</html>

RSS

Introduction to RSS

« Previous Next Chapter »

What You Should Already Know

Before you continue you should have a basic understanding of the following:

  • HTML / XHTML
  • XML / XML Namespaces

If you want to study these subjects first, find the tutorials on our Home page.


What is RSS?

  • RSS stands for Really Simple Syndication
  • RSS allows you to syndicate your site content
  • RSS defines an easy way to share and view headlines and content
  • RSS files can be automatically updated
  • RSS allows personalized views for different sites
  • RSS is written in XML

Why use RSS?

RSS was designed to show selected data.

Without RSS, users will have to check your site daily for new updates. This may be too time-consuming for many users. With an RSS feed (RSS is often called a News feed or RSS feed) they can check your site faster using an RSS aggregator (a site or program that gathers and sorts out RSS feeds).

Since RSS data is small and fast-loading, it can easily be used with services like cell phones or PDA’s.

Web-rings with similar information can easily share data on their web sites to make them better and more useful.


Who Should use RSS?

Webmasters who seldom update their web sites do not need RSS!

RSS is useful for web sites that are updated frequently, like:

  • News sites – Lists news with title, date and descriptions
  • Companies – Lists news and new products
  • Calendars – Lists upcoming events and important days
  • Site changes – Lists changed pages or new pages

The Future of RSS

Thousands of sites use RSS, and more people understand its usefulness every day.

With RSS, information on the internet becomes easier to find, and web developers can spread their information more easily.


Benefits of RSS

 

Choose your news
With RSS you can choose to view the news you want, the news that interest you and are relevant to your work.

 

 

Remove unwanted information
With RSS you can (finally) separate wanted information from unwanted information (spam)!

 

 

Increase your site traffic
With RSS you can create your own news channel, and publish

History of RSS

« Previous Next Chapter »

RSS has been released in many different versions.


The History of RSS

  • 1997 – Dave Winer develops scriptingNews. RSS was born.
     
  • 1999 – Netscape develops RSS 0.90 (which supported scriptingNews). This was simply XML with an RDF Header.
     
  • 1999 – Dave Winer at UserLand develops scriptingNews 2.0b1 (This included Netscape’s RSS 0.90 features)
     
  • 1999 – Netscape develops RSS 0.91. In this version they removed the RDF header, but included most features from scriptingNews 2.0b1.
     
  • 1999 – UserLand gets rid of scriptingNews and uses only RSS 0.91
     
  • Netscape stops their RSS development
     
  • 2000 – UserLand releases the official RSS 0.91 specification
     
  • 2000 – A group lead by Rael Dornfest at O’Reilly develops RSS 1.0. This format uses RDF and namespaces. This version is often confused as being a new version of 0.91, but this is a completely new format with no ties to RSS 0.91
     
  • 2000 – Dave Winer at UserLand develops RSS 0.92
     
  • 2002 – Dave Winer develops RSS 2.0 after leaving Userland
     
  • 2003 – The official RSS 2.0 specification is released

What are the Differences?

RSS 1.0 is the only version that was developed using the W3C RDF (Resource Description Framework) standard.

The idea behind RDF was to help create a Semantic Web. Read more about RDF and the Semantic Web here. However, this does not matter too much for ordinary users, but by using web standards it will be easier for persons and applications to exchange data.


What RSS Version Should I Use?

RSS 0.91 and RSS 2.0 are easier to understand than RSS 1.0. Our tutorial is based on RSS 2.0.


Is There an RSS Web Standard?

There is no official standard for RSS.

  • About 50 % of all RSS feeds use RSS 0.91
  • About 25 % use RSS 1.0
  • The last 25 % is split between RSS 0.9x versions and RSS 2.0

RSS Syntax

« Previous Next Chapter »

The syntax rules of RSS 2.0 are very simple and very strict.


How RSS Works

RSS is used to share content between websites.

With RSS, you register your content with companies called aggregators.

So, to be a part of it: First, create an RSS document and save it with an .xml extension. Then, upload the file to your website. Next, register with an RSS aggregator. Each day the aggregator searches the registered websites for RSS documents, verifies the link, and displays information about the feed so clients can link to documents that interests them.

Tip: Read our RSS Publishing chapter to view free RSS aggregation services.


RSS Example

RSS documents use a self-describing and simple syntax.

Here is a simple RSS document:

<?xml version=”1.0″ encoding=”ISO-8859-1″ ?>
<rss version=”2.0″>

<channel>
  <title>W3Schools Home Page</title>
  <link>http://www.w3schools.com</link&gt;
  <description>Free web building tutorials</description>
  <item>
    <title>RSS Tutorial</title>
    <link>http://www.w3schools.com/rss</link&gt;
    <description>New RSS tutorial on W3Schools</description>
  </item>
  <item>
    <title>XML Tutorial</title>
    <link>http://www.w3schools.com/xml</link&gt;
    <description>New XML tutorial on W3Schools</description>
  </item>
</channel>

</rss>

The first line in the document – the XML declaration – defines the XML version and the character encoding used in the document. In this case the document conforms to the 1.0 specification of XML and uses the ISO-8859-1 (Latin-1/West European) character set.

The next line is the RSS declaration which identifies that this is an RSS document (in this case, RSS version 2.0).

The next line contains the <channel> element. This element is used to describe the RSS feed.

The <channel> element has three required child elements:

  • <title> – Defines the title of the channel (e.g. W3Schools Home Page)
  • <link> – Defines the hyperlink to the channel (e.g. http://www.w3schools.com)
  • <description> – Describes the channel (e.g. Free web building tutorials)

Each <channel> element can have one or more <item> elements.

Each <item> element defines an article or “story” in the RSS feed.

The <item> element has three required child elements:

  • <title> – Defines the title of the item (e.g. RSS Tutorial)
  • <link> – Defines the hyperlink to the item (e.g. http://www.w3schools.com/rss)
  • <description> – Describes the item (e.g. New RSS tutorial on W3Schools)

Finally, the two last lines close the <channel> and <rss> elements.


Comments in RSS

The syntax for writing comments in RSS is similar to that of HTML:

<!– This is an RSS comment –>

 


RSS is Written in XML

Because RSS is XML, keep in mind that:

  • All elements must have a closing tag
  • Elements are case sensitive
  • Elements must be properly nested
  • Attribute values must always be quoted

RSS <channel> Element

« Previous Next Chapter »

The RSS <channel> element describes the RSS feed.


The RSS <channel> Element

Look at the following RSS document:

<?xml version=”1.0″ encoding=”ISO-8859-1″ ?>
<rss version=”2.0″>

<channel>
  <title>W3Schools Home Page</title>
  <link>http://www.w3schools.com</link&gt;
  <description>Free web building tutorials</description>
  <item>
    <title>RSS Tutorial</title>
    <link>http://www.w3schools.com/rss</link&gt;
    <description>New RSS tutorial on W3Schools</description>
  </item>
</channel>

</rss>

As mentioned before, the <channel> element describes the RSS feed, and has three required child elements:

  • <title> – Defines the title of the channel (e.g. W3Schools Home Page)
  • <link> – Defines the hyperlink to the channel (e.g. http://www.w3schools.com)
  • <description> – Describes the channel (e.g. Free web building tutorials)

The <channel> element usually contains one or more <item> elements. Each <item> element defines an article or “story” in the RSS feed.

Furthermore, there are several optional child elements of <channel>. We will explain the most important ones below.


The <category> Element

The <category> child element is used to specify a category for your feed.

The <category> element makes it possible for RSS aggregators to group sites based on category.

The category for the RSS document above could be:

<category>Web development</category>

 


The <copyright> Element

The <copyright> child element notifies about copyrighted material.

The copyright for the RSS document above could be:

<copyright>2006 Refsnes Data as. All rights reserved.</copyright>

 


The <image> Element

The <image> child element allows an image to be displayed when aggregators present a feed.

The <image> element has three required child elements:

  • <url> – Defines the URL to the image
  • <title> – Defines the text to display if the image could not be shown
  • <link> – Defines the hyperlink to the website that offers the channel

The image for the RSS document above could be:

<image>
  <url>http://www.w3schools.com/images/logo.gif</url&gt;
  <title>W3Schools.com</title>
  <link>http://www.w3schools.com</link&gt;
</image>

 


The <language> Element

The <language> child element is used to specify the language used to write your document.

The <language> element makes it possible for RSS aggregators to group sites based on language.

The language for the RSS document above could be:

<language>en-us</language>

 


RSS <channel> Reference

Element Description
<category> Optional. Defines one or more categories for the feed
<cloud> Optional. Register processes to be notified immediately of updates of the feed
<copyright> Optional. Notifies about copyrighted material
<description> Required. Describes the channel
<docs> Optional. Specifies an URL to the documentation of the format used in the feed
<generator> Optional. Specifies the program used to generate the feed
<image> Optional. Allows an image to be displayed when aggregators present a feed
<language> Optional. Specifies the language the feed is written in
<lastBuildDate> Optional. Defines the last-modified date of the content of the feed
<link> Required. Defines the hyperlink to the channel
<managingEditor> Optional. Defines the e-mail address to the editor of the content of the feed
<pubDate> Optional. Defines the last publication date for the content of the feed
<rating> Optional. The PICS rating of the feed
<skipDays> Optional. Specifies the days where aggregators should skip updating the feed
<skipHours> Optional. Specifies the hours where aggregators should skip updating the feed
<textInput> Optional. Specifies a text input field that should be displayed with the feed
<title> Required. Defines the title of the channel
<ttl> Optional. Specifies the number of minutes the feed can stay cached before refreshing it from the source
<webMaster> Optional. Defines the e-mail address to the webmaster of the feed

RSS <item> Element

« Previous Next Chapter »

Each <item> element defines an article or “story” in an RSS feed.


The <item> Element

Look at the following RSS document:

<?xml version=”1.0″ encoding=”ISO-8859-1″ ?>
<rss version=”2.0″>

<channel>
  <title>W3Schools Home Page</title>
  <link>http://www.w3schools.com</link&gt;
  <description>Free web building tutorials</description>
  <item>
    <title>RSS Tutorial</title>
    <link>http://www.w3schools.com/rss</link&gt;
    <description>New RSS tutorial on W3Schools</description>
  </item>
</channel>

</rss>

As mentioned before, each <item> element defines an article or “story” in the RSS feed.

The <item> element has three required child elements:

  • <title> – Defines the title of the item (e.g. RSS Tutorial)
  • <link> – Defines the hyperlink to the item (e.g. http://www.w3schools.com/rss)
  • <description> – Describes the item (e.g. New RSS tutorial on W3Schools)

Furthermore, there are several optional child elements of <item>. We will explain the most important ones below.


The <author> Element

The <author> child element is used to specify the e-mail address of the author of an item.

Note: To prevent spam e-mails, some developers do not include the <author> element.

The author of the item in the RSS document above could be:

<author>hege@refsnesdata.no</author>

 


The <comments> Element

The <comments> child element allows an item to link to comments about that item.

A comment of the item in the RSS document above could be:

<comments>http://www.w3schools.com/comments</comments&gt;

 


The <enclosure> Element

The <enclosure> child element allows a media-file to be included with an item.

The <enclosure> element has three required attributes:

  • url – Defines the URL to the media file
  • length – Defines the length (in bytes) of the media file
  • type – Defines the type of media file

A media-file included in the item in the RSS document above could be:

<enclosure url=”http://www.w3schools.com/rss/rss.mp3&#8243;
length=”5000″ />

 


RSS <item> Reference

Element Description
<author> Optional. Specifies the e-mail address to the author of the item
<category> Optional. Defines one or more categories the item belongs to
<comments> Optional. Allows an item to link to comments about that item
<description> Required. Describes the item
<enclosure> Optional. Allows a media file to be included with the item
<guid> Optional. Defines a unique identifier for the item
<link> Required. Defines the hyperlink to the item
<pubDate> Optional. Defines the last-publication date for the item
<source> Optional. Specifies a third-party source for the item
<title> Required. Defines the title of the item

RSS Publish Your Feed

« Previous Next Chapter »

Having an RSS document is not useful if other people cannot reach it.


Get Your RSS Feed Up On The Web

Now it’s time to get your RSS file up on the web. Here are the steps:

1. Name your RSS file. Notice that the file must have an .xml extension.

2. Validate your RSS file (a good validator can be found at http://www.feedvalidator.org).

3. Upload the RSS file to your web directory on your web server.

4. Copy the little orange or button to your web directory.

5. Put the little orange “RSS” or “XML” button on the page where you will offer RSS to the world (e.g. on your home page). Then add a link to the button that links to the RSS file. The code will look something like this:
<a href=”www.w3schools.com/rss/myfirstrss.xml”>
< img src=”www.w3schools.com/rss/rss.gif” width=”36″ height=”14″>
</a>.

6. Submit your RSS feed to the RSS Feed Directories (you can Google or Yahoo for “RSS Feed Directories”). Note! The URL to your feed is not your home page, it is the URL to your feed, like “http://www.w3schools.com/rss/myfirstrss.xml&#8221;. Here are some free RSS aggregation services:

7. Register your feed with the major search engines:

8. Update your feed – Now you have registered your RSS feed with Google, Yahoo, and MSN. Now you must make sure that you update your content frequently and that your RSS feed is constantly available.


Can I Manage my RSS Feed Myself?

The best way to ensure your RSS feed works the way you want, is to manage it yourself.

However, this can be very time consuming, especially for pages with lot of updates.

An alternative is to use a third-party automated RSS.


Automated RSS

If you don’t want to update your RSS feed yourself, there are tools and services that can do it automatically for you, such as:

  • MyRSSCreator – offers an automated, reliable RSS service in just 10 minutes
  • FeedFire – offers free creation and distribution of RSS feeds

For users who only need an RSS feed for their personal website, some of the most popular blog (Web Log) managers that offer built-in RSS services are:

RSS Readers

« Previous Next Chapter »

An RSS Reader is used to read RSS Feeds!

RSS readers are available for many different devices and OS.


RSS Readers

There are a lot of different RSS readers. Some work as web services, and some are limited to windows (or Mac, PDA or UNIX). Here are a few I have tried and liked:

  • RssReader – A free Windows-based RSS reader. Supports RSS versions 0.9x, 1.0 and 2.0 and Atom 0.1, 0.2 and 0.3.
  • FeedDemon – A Windows-based RSS reader. Very easy to use and has a very orderly interface.
  • blogbot – An RSS reader plug-in for Outlook or Internet Explorer. The light-version for Internet Explorer is free.

Tip: The Mozilla Firefox browser has a built-in RSS Reader. If you go to a web site that offers RSS feeds, you will see the Firefox RSS icon in the address bar. Click on the icon to view a list of the different feeds. Choose the feed you want to read.


I have an RSS Reader. Now what?

Click on the little or button next to the RSS feed you want to read. Copy The URL you get in the browser window and paste it in your RSS reader.

RSS Reference

« Previous Next Chapter »

RSS <channel> Element

The links in the “Element” column point to more information about each specific element.

Element Description
<category> Optional. Defines one or more categories for the feed
<cloud> Optional. Register processes to be notified immediately of updates of the feed
<copyright> Optional. Notifies about copyrighted material
<description> Required. Describes the channel
<docs> Optional. Specifies an URL to the documentation of the format used in the feed
<generator> Optional. Specifies the program used to generate the feed
<image> Optional. Allows an image to be displayed when aggregators present a feed
<language> Optional. Specifies the language the feed is written in
<lastBuildDate> Optional. Defines the last-modified date of the content of the feed
<link> Required. Defines the hyperlink to the channel
<managingEditor> Optional. Defines the e-mail address to the editor of the content of the feed
<pubDate> Optional. Defines the last publication date for the content of the feed
<rating> Optional. The PICS rating of the feed
<skipDays> Optional. Specifies the days where aggregators should skip updating the feed
<skipHours> Optional. Specifies the hours where aggregators should skip updating the feed
<textInput> Optional. Specifies a text input field that should be displayed with the feed
<title> Required. Defines the title of the channel
<ttl> Optional. Specifies the number of minutes the feed can stay cached before refreshing it from the source
<webMaster> Optional. Defines the e-mail address to the webmaster of the feed

RSS <item> Element

Element Description
<author> Optional. Specifies the e-mail address to the author of the item
<category> Optional. Defines one or more categories the item belongs to
<comments> Optional. Allows an item to link to comments about that item
<description> Required. Describes the item
<enclosure> Optional. Allows a media file to be included with the item
<guid> Optional. Defines a unique identifier for the item
<link> Required. Defines the hyperlink to the item
<pubDate> Optional. Defines the last-publication date for the item
<source> Optional. Specifies a third-party source for the item
<title> Required. Defines the title of the item

 

Bảo vệ: Bài tập Pascal_Giải(Phần I)

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Bài tập Pascal

BÀI TẬP NGÔN NGỮ LẬP TRÌNH PASCAL
I. Vẽ lưu đồ giải thuật:
1. Nhập vào hai số x, y. Xuất ra màn hình tổng, hiệu, tích, thương của hai số trên.
2. Nhập vào số nguyên n, kiểm tra xem n chẵn hay lẻ và xuất ra màn hình.
3. Nhập vào ba cạnh a, b, c của tam giác. Xuất ra màn hình tam giác đó thuộc loại tam giác gì? (Thường, cân, vuông, đều hay vuông cân).
4. Nhập vào số nguyên n. Xuất n ra màn hình (Nếu n chẵn thì gấp đôi giá trị).
5. Nhập vào số nguyên n. Nếu n>5 thì tăng n lên 2 đơn vị và trả về giá trị n, ngược lại trả về giá trị 0.
6. Tính n!, Với n 0
7. Tính P(n) = 1.3.5…(2n+1), Với n 0
8. Tính S(n) = 1+3+5+…+(2 n +1), Với n 0
9. Tính S(n) = 1-2+3-4+…+(-1)n+1 n, Với n >0
10. Tính S(n) =1+1.2+1.2.3+…+1.2.3…n, Với n >0
11. Tính S(n) =12+22+32+…+n2, Với n >0
12. Tính S(n) = 1+ + +…+ , Với n >0
13. (*) Tính S(n) = 1+ + +…+ , Với n >0
14. Tính P(x, y) = xy.
15. Tính S(n) = 1+(1+2)+(1+2+3)+…+(1+2+3+…+n), Với n >0
16. Cho số nguyên n. Tính trị tuyệt đối của n.
17. Cho số nguyên dương n gồm k chữ số. Tìm chữ số có giá trị lớn nhất.
18. Đếm số lượng ước số chẵn của số nguyên dương n.
19. In ra chữ số đầu tiên của số nguyên dương n gồm k chữ số.
20. Cho 2 số nguyên dương a, b. Tìm ước số chung lớn nhất của a và b.
21. Cho 2 số nguyên dương a, b. Tìm bội số chung nhỏ nhất của a và b.
22. Cho số nguyên dương x. Kiểm tra xem x có phải là số nguyên tố không?
23. Cho số nguyên dương x. Kiểm tra xem x có phải là số chính phương không?
24. Cho số nguyên dương x. Kiểm tra xem x có phải là số hoàn thiện không?
25. Tính S(n) = 1+ 22+33+…+nn, Với n 0
26. Tính S(n) = + + +…+ , Với n >0
27. Tính S(n) = 1+ + +…+ , Với n >0
28. Tính S(n) = 1+ + +…+ , Với n >0
29. Giải và biện luận phương trình: ax2 +bx +c =0
30. Giải và biện luận phương trình: ax4 +bx2 +c =0
31. (*) Tính S(n) = , Với n >0
32. (**) Tính S(n) = , Với n >0
II. Cấu trúc if / if…else và case
1. Nhập vào hai số nguyên a, b. In ra màn hình giá trị lớn nhất.
2. Cho ba số a, b, c đọc vào từ bàn phím. Hãy tìm giá trị lớn nhất của ba số trên và in ra kết quả.
3. Cho ba số a, b, c đọc vào từ bàn phím. Hãy in ra màn hình theo thứ tự tăng dần các số. (Chỉ được dùng thêm 2 biến phụ).
4. Viết chương trình nhập vào một số nguyên n gồm 3 chữ số. Xuất ra màn hình chữ số lớn nhất ở vị trí nào?
Ví dụ: n=291. Chữ số lớn nhất nằm ở hàng chục (9).
5. Viết chương trình nhập vào một số nguyên n gồm 3 chữ số. Xuất ra màn hình theo thứ tự tăng dần của các chữ số.
Ví dụ: n=291. Xuất ra 129.
6. Nhập vào ngày, tháng, năm. Kiểm tra xem ngày, tháng, năm đó có hợp lệ hay không? In kết quả ra màn hình.
7. Nhập vào giờ, phút, giây. Kiểm tra xem giờ, phút, giây đó có hợp lệ hay không? In kết quả ra màn hình.
8. Viết chương trình nhập vào ngày, tháng, năm hợp lệ. Cho biết năm này có phải là năm nhuần hay không? In kết quả ra màn hình.
9. Viết chương trình tính diện tích và chu vi các hình: tam giác, hình vuông, hình chữ nhật và hình tròn với những thông tin cần được nhập từ bàn phím.
10. Viết chương trình tính tiền cước TAXI. Biết rằng:
 KM đầu tiên là 5000đ
 200m tiếp theo là 1000đ
 Nếu lớn hơn 20km thì mỗi km thêm sẽ là 3000đ
 Hãy nhập số km sau đó in ra số tiền phải trả.
11. Nhập vào 3 số nguyên dương a, b, c. Kiểm tra xem 3 số đó có lập thành tam giác hay không? Nếu có hãy cho biết tam giác đó thuộc loại nào? (Cân, vuông, đều,…).
12. Viết chương trình nhập vào số nguyên dương n. Kiểm tra xem n có phải là số chính phương hay không? ( Số chính phương là số khi lấy căn bậc 2 có kết quả là nguyên).
III. Cấu trúc lặp
1. Cho biết kết quả của đoạn chương trình sau:
a:=18;
for i:=1 to a do
if (a mod i = 0) then
write(i, ‘ ’);
2. Cho biết kết quả của đoạn chương trình sau:
for i:=1 to 5 do
Begin
for j:=1 to i do
write(j, ‘ ’);
writeln;
End;

3. Cho biết kết quả của đoạn chương trinh sau:
i:= 10; s:=0;
while (i>0) do
Begin
if (i mod 2 =0) then
s:=s+i
else
if (i>5) then
s:=s+2*i;
i:=i-1;
End;
writeln(‘s= ’, s); 4. Cho biết kết quả của đoạn chương trình sau:
a:=18; i:=1;
Repeat
if (a mod i=0) then
write(i, ‘ ’);
i:=i+1;
Until( i>a);

5. Cho biết kết quả của đoạn chương trình sau:
a:=11; b:=16; i:=a;
while( i<b) do
Begin
if (i mod 2=0) then
Begin
write(i, ‘ ’);
break;
End;
i:=i+1;
End;
6. Cho biết kết quả của đoạn chương trình sau:
a:=10; s:=0; i:=0;
while (i<a) do
Begin
i:=i+1;
if (i mod 2=0) then
continue
else
s:=s+i;
End;
writeln(s, ‘ ’);

7. Cho biết kết quả của đoạn chương trình sau:
i:=1: s:=0;
while(True)
Begin
s:= s+i;
i:=i+1;
if(i mod 2 0) then
i:=i+2
else
i:=i+1;
if (i>20) then
break;
End;
writeln(s, ‘ ’);

8. Viết chương trình in ra màn hình hình chữ nhật đặc kích thước m x n (m, n nhập từ bàn phím).
Ví dụ: Nhập m=5, n=4
* * * * *
* * * * *
* * * * *
* * * * *
9. Viết chương trình in ra màn hình hình chữ nhật rỗng kích thước m x n (m, n nhập từ bàn phím).
Ví dụ: Nhập m=5, n=4
* * * * *
* *
* *
* * * * *
10. Viết chương trình in ra màn hình tam giác vuông cân đặc có độ cao h (h nhập từ bàn phím).
Ví dụ: Nhập h=4
*
* *
* * *
* * * *
11. Viết chương trình in ra màn hình tam giác cân rỗng có độ cao h (h nhập từ bàn phím).
Ví dụ: Nhập h=4
*
* *
* *
* * * *
12. Viết chương trình in ra màn hình tam giác cân đặc có độ cao h (h nhập từ bàn phím).
Ví dụ: Nhập h=4
*
* * *
* * * * *
* * * * * * *

13. Viết chương trình in ra màn hình tam giác cân rỗng có độ cao h (h nhập từ bàn phím).
Ví dụ: Nhập h=4
*
* *
* *
* * * * * * *
14. Viết chương trình nhập số nguyên dương n. Liệt kê n số nguyên tố đầu tiên.
15. Viết chương trình nhập vào hai số nguyên dương a và b. Tìm ước số chung lớn nhất và bội số chung nhỏ nhất của a và b.
16. Viết chương trình nhập vào 1 số nguyên n gồm tôi đa 10 chữ số (a bytes). In ra màn hình giá trị nhị phân của số trên. (Hướng dẫn: Chia lấy dư cho 2 và xuất theo thứ tự ngược lại dùng hàm gotoxy, wherex, wherey).
17. Viết chương trình đếm ước số của số nguyên dương N.
Ví dụ: N=12
số ước số của 12 là 6.
18. Một số hoàn thiện là 1 số có tổng các ước số của nó (không kể nó) bằng chính nó. Hãy liệt kê các số hoàn thiện nhỏ hơn 5000.
Ví dụ: số 6 là số hoàn thiện vì tổng các ước số là 1+2+3=6.
19. Nhập vào ngày, tháng, năm. Cho biết đó là ngày thứ mấy trong năm.
20. In ra dãy số Fibonaci
f1=f0=1;
fn=f n-1+f n-2; (n>1)
IV. Phần chuỗi ký tự
1. Viết chương trình nhập vào một chuỗi ký tự, đếm số ký tự có trong chuỗi.
2. Viết chương trình đếm có bao nhiêu khoảng trắng trong chuỗi.
3. Viết chương trình nhập vào một chuỗi, hãy loại bỏ những khoảng trắng thừa trong chuỗi.
4. Viết chương trình nhập vào hai chuỗi s1 và s2, nối chuỗi s2 vào s1. Xuất chuỗi s1 ra màn hình.
5. Đổi tất cả các ký tự có trong chuỗi thành chữ thường.
6. Đổi tất cả các ký tự trong chuỗi sang chữ hoa.
7. Viết chương trình đổi những ký tự đầu tiên của mỗi từ thành chữ hoa.
8. Viết chương trình đổi chữ xen kẽ 1 chữ hoa và 1 chữ thường.
Ví dụ: nhập ABCDEfgh đổi thành AbCdEfGh
9. Viết chương trình đảo ngược các ký tự trong chuỗi.
Ví dụ: nhập ABCDE, xuất ra màn hình là: EDCBA
10. Viết chương trình tìm kiếm 1 ký tự có trong chuỗi hay không, nếu có xuất ra vị trí của từ đó.
11. Viết 1 chương trình đếm một ký tự xuất hiện bao nhiêu lần trong chuỗi.
12. Viết chương trình tìm kiếm tên trong chuỗi họ tên. Nếu có thì xuất ra là tên này đã nhập đúng, ngược lại thông báo là đã nhập sai.
13. Viết chương trình đảo vị trí của từ đầu và từ cuối.
Ví dụ: nhập ‘bo an co’ xuat ra ‘co an bo’
14. Viết chương trình con cắt chuỗi họ tên thành chuỗi họ lót và chuỗi tên.
Ví du: chuỗi họ tên là: ‘Nguyen Van A’ cắt ra 2 chuỗi là họ lót: ‘Nguyen Van’, chuỗi tên là: ‘A’
15. Nhập một chuỗi bất kỳ, sau đó hỏi người dùng cần tách bắt đầu từ đâu trong chuỗi trở về sau.
Ví dụ: nhập chuỗi S1: ‘Truong Cao Đang Cong Thuong’. Người nhập muốn tách bắt đầu từ chữ ‘Cong’ thì sẽ xuất ra chuỗi ‘Cong Thuong’ ra màn hình.
16. Viết chương trình con kiểm tra xem chuỗi có đối xứng hay không?
17. Viết chương trình con kiểm tra xem trong chuỗi có ký tự số hay không nếu có tách ra thành một mảng số riêng.
18. Nhập một chuỗi bất kỳ, yêu cầu nhập 1 ký tự muốn xóa. Thực hiện xóa tất cả những ký tự đó trong chuỗi.
19. Viết chương trình tìm kiếm xem ký tự nào xuất hiện nhiều nhất trong chuỗi.
20. Viết chương trình xóa một cụm từ nào đó trong chuỗi.
Ví dụ: Chuỗi ban đầu: ‘Cao Dang Cong Thuong’
Nhập: ‘Cong Thuong’, và kết quả xuất ra là ‘Cao Dang ‘
21. Đổi các từ đầu mỗi từ sang chữ hoa và những từ không phải đầu mỗi từ sang chữ thường.
Ví dụ: nGuYen vAN a đổi thành Nguyen Van A
22. (*) Viết chương trình đảo ngược thứ tự các từ có trong chuỗi
Ví dụ: Nhập Truong CD Cong Thuong TpHCM
Xuất ra màn hình là: TpHCM Thuong Cong CD Truong
23. Nhập 1 chuỗi bất kỳ, liệt kê xem mỗi ký tự xuất hiện mấy lần.
24. Viết chương trình con kiểm tra xem trong 2 chuỗi có bao nhiêu ký tự giống nhau.
25. Viết chương trình chạy từ trái qua phải màn hình.
26. Viết 1 chương trình chèn 1 từ ở bất cứ vị trí nào mà người dùng yêu cầu.
27. (*) Viết chương trình nhập vào một chuỗi đếm xem chuỗi có bao nhiêu từ. Các từ cách nhau bằng khoảng trắng, dấu chấm câu: dấu chấm(.), dấu phẩy (,), dấu chấm phẩy (;), dấu hỏi(?) và dấu chấm than (!).
28. (**) Viết chương trình hiển thị một chuỗi ký tự. Chương trình cho phép di chuyển dấu nháy sang trái, sang phải, lên dòng hay xuống dòng bằng phím mũi tên, chèn hay xóa ký tự tại vị trí dấu nháy.
V. Phần mảng một chiều
1. Viết chương trình nhập xuất mảng 1 chiều các số thực.
2. Viết chương trình khởi tạo giá trị phần tử là 0 cho mảng 1 chiều các số nguyên gồm n phần tử.
3. Viết chương trình phát sinh ngẫu nhiên mảng 1 chiều các số nguyên âm.
4. Viết chương trình phát sinh ngẫu nhiên mảng một chiều các số nguyên sao cho mảng có thứ tự tăng (không càn sắp xếp).
5. Viết chương trình nhập mảng các số thực và xuất các phần tử âm trong mảng.
6. Viết chương trình nhập mảng các số nguyên và xuất các phần tử lẻ có trong mảng.
7. Viết chương trình nhập vào mảng một chiều các số nguyên và xuát ra các phần tử chẵn nhỏ hơn 20.
8. Viết chương trình nhập vào mảng 1 chiều các số nguyên và xuất ra màn hình các phần tử là số nguyên tố.
9. Viết chương trình nhập vào số nguyên n và liệt kê các số nguyên nhỏ hơn n, nếu mảng không tồn tại số nguyên tố nào nhỏ hơn n thì phải xuất ra một câu thông báo.
10. Viết chương trình nhập vào mảng một chiều các số nguyên và xuất ra màn hình các phần tử là số chính phương nằm tại những vị trí lẻ trong mảng.
11. Viết chương trình con tìm vị trí phần tử có giá trị x xuất hiện cuối cùng trong mảng.
12. Viết chương trình con tìm vị trí của phần tử nhỏ nhất trong mảng các số nguyên.
13. Viết chương trình con tìm vị trí của phần tử lớn nhất trong mảng các số nguyên.
14. Viết chương trình con in vị trí của các phần tử nguyên tố trong mảng các số nguyên.
15. Viết chương trình con in vị trí của các phần tử nguyên tố lớn hơn 23.
16. Viết chương trình con tìm vị trí phần tử âm đầu tiên trong mảng. Nếu không có phần tử âm trả về -1.
17. Viết chương trình con tìm vị trí phần tử lớn nhất trong mảng.
18. Viết chương trình con tìm vị trí phần tử dương đầu tiên trong mảng. Nếu không có phần tử âm trả về -1.
19. Viết chương trình con tìm vị trí phần tử dương bé nhất trong mảng.
20. Viết chương trình con in các phần tử là bội của 3 và 5.
21. Viết chương trình con tìm số chẵn cuối cùng có trong mảng, nếu không tồn tại số chẵn chương trình con trả về -1.
22. Viết chương trình con tìm số lẻ lớn nhất có trong mảng, nếu không tồn tại số lẻ chương trình con trả về -1.
23. Viết chương trình con tìm và đổi chỗ phần tử lớn nhất với phần tử nhỏ nhất trong mảng.
24. Nhập vào X. Viết chương trình con in ra màn hình những phần tử có giá trị từ 1 đến X có trong mảng.
25. Viết chương trình nhập vào một dãy số a gồm n số thực (n 100), nhập vào dãy số b gồm m số thực (m 100).
 In ra những phần tử chỉ xuất hiện trong dãy a mà không xuất hiện trong dãy b.
 In ra những phần tử xuất hiện ở cả 2 dãy.
26. Viết chương trình con đếm các phần tử âm, dương trong mảng.
27. Viết chương trình con đếm các phần tử chẵn, lẻ trong mảng.
28. Viết chương trình con đếm số lần xuất hiện của phần tử x trong mảng.
29. Viết chương trình con đếm các phần tử nhỏ hơn x trong mảng.
30. Viết chương trình con đếm các phần tử là số nguyên tố trong mảng.
31. Viết chương trình con đếm các phần tử là số hoàn thiện trong mảng.
32. Viết chương trình con đếm các phần tử là bội của 3 và 5 trong mảng các số nguyên.
33. Viết chương trình con tính tổng các phần tử chẵn trong mảng.
34. Viết chương trình con tính tổng các phần tử lẻ trong mảng các số nguyên.
35. Viết chương trình con tính tổng các phần tử nguyên tố trong mảng.
36. Viết chương trình con tính tổng các phần tử nằm ở vị trí chẵn trong mảng các số nguyên.
37. Viết chương trình con tính tổng các phần tử nằm ở vị trí nguyên tố trong mảng.
38. Viết chương trình con tính tổng các phần tử chia hết cho 5 có trong mảng.
39. Viết chương trình con tính tổng các phần tử cực đại trong mảng các số nguyên (phần tử cực đại là phần tử lớn hơn các phần tử xung quanh nó).
Ví dụ: 1 5 2 6 3 5 1 8 6
40. Viết chương trình con tính tổng các phần tử cực tiểu trong mảng các số nguyên (phần tử cực tiểu là phần tử nhỏ hơn các phần tử xung quanh nó).
Ví dụ: 6 4 2 9 5 3 7 1 5 8
41. Viết chương trình con tính tổng các phần tử là bội của 3 và 5 trong mảng các số nguyên.
42. Viết chương trình con tính tổng các phần tử là số hoàn thiện trong mảng các số nguyên.
43. Viết chương trình con tính giá trị trung bình của các số hoàn thiện trong mảng các số nguyên.
44. Viết chương trình con sắp xếp mảng theo thứ tự giảm dần.
45. Viết chương trình con sắp xếp mảng theo thứ tự tăng dần của các phần tử là số nguyên tố.
46. Viết chương trình con sắp xếp các phần tử lẻ tăng dần.
47. Viết chương trình con sắp xếp các phần tử chẵn giảm dần.
48. Viết chương trình con sắp xếp các phần tử chẵn nằm bên trái theo thứ tự tăng dần còn các phần tử lẻ bên phải theo thứ tự giảm dần.
49. Viết chương trình con sắp xếp các phần tử âm giảm dần từ trái sang phải, phần tử dương tăng dần từ phải sang trái.
50. Viết chương trình con xóa phần tử tại vị trí lẻ trong mảng.
51. Viết chương trình con xóa phần tử có giá trị lớn nhất trong mảng.
52. Nhập vào giá trị X. Viết chương trình con xóa tất cả các phần tử có giá trị nhỏ hơn X.
53. Nhập vào giá trị X. Viết chương trình con xóa phần tử có giá trị gần X nhất.
54. Viết chương trình con chèn phần tử có giá trị X vào vị trí đầu tiên của mảng.
55. Viết chương trình con chèn phần tử có giá trị X vào phía sau phần tử có giá trị lớn nhất trong mảng.
56. Viết chương trình con chèn phần tử có giá trị X vào trước phần tử có giá trị là số nguyên tố đầu tiên trong mảng.
57. Viết chương trình con chèn phần tử có giá trị X vào phía sau tất cả các phần tử có giá trị chẵn trong mảng.
58. Viết chương trình tách 1 mảng các số nguyên thành 2 mảng a và b, sao cho mảng a chứa toàn số lẻ và mảng b chứa toàn số chẵn.
Ví dụ: Mảng ban đầu: 1 3 8 2 7 5 9 0 10
Mảng a: 1 3 7 5 9
Mảng b: 8 2 10

59. Cho 2 mảng số nguyên a và b kích thước lần lượt là n và m. Viết chương trình nối 2 mảng trên thành mảng c theo nguyên tắc chẵn ở đầu mảng và lẻ ở cuối mảng.
Ví dụ: Mảng a: 3 2 7 9
Mảng b: 1 8 10 4 12 6
Mảng c: 6 12 4 10 2 8 3 1 7 5 9
60. Viết chương trình nhập vào mảng A gồm n phần tử, trong quá trình nhập kiểm tra các phần tử nhập vào không được trùng, nếu trùng thông báo và yêu cầu nhập lại.
61. Viết chương trình con tính tổng của từng dãy con giảm có trong mảng.
62. (*) Cho mảng các số nguyên a gồm n phần tử (n 30000) và số dương k (k n). Hãy chỉ ra số hạng lớn thứ k của mảng.
Ví dụ: Mảng a: 6 3 1 10 11 18
k=2
Kết quả: 10
63. (*) Cho 2 dãy A, B các số nguyên (kích thước dãy A nhỏ hơn dãy B). Hãy kiểm tra xem A có phải là con của B hay không?
64. Viết chương trình con liệt kê các bộ 4 số a, b, c, d trong mảng các số nguyên (có ít nhất 4 phần tử và đôi một khác nhau) sao cho a+b =c+d.
65. (*) Viết chương trình tính trung bình cộng của các tổng các dãy tăng dần có trong mảng các số nguyên.
Ví dụ: 1 2 3 4 2 3 5 6 4 5 6 TB =15
66. Viết chương trình tính tổng tất cả các phần tử xung quanh trên mảng các số nguyên. (Phần tử xung quanh là 2 phần tử bên cạnh cộng lại bằng chính nó. Ví dụ: 1 2 3 1,2 là 2 phần tử xung quanh của 3).
Ví dụ: 1 3 2 5 3 9 6 Tổng 17
67. (**) Viết chương trình nhập vào 2 số lớn a, b nguyên (a, b từ 20 chữ số trở lên). Tính tổng, hiệu, tích, thương của 2 số trên.
68. Viết chương trình con tính tổng các phần tử là số Amstrong (số Amstrong là số có đặc điểm như sau: số có k ký số, tổng của các lũy thừa bậc k của các ký số bằng chính số đó).
Ví dụ: 153 là số có các ký số 13+53+33 =153 là một số Amstrong
69. Viết chương trình con tìm và xóa tất cả các phần tử trùng với x trong mảng 1 chiều các số nguyên, nếu không tồn tại phần tử x trong mảng thì trả về -1.
70. Viết chương trình con xóa tất cả những phần tử trùng nhau trong dãy chỉ giữ lại một phần tử trong đó.
Ví dụ: 1 6 2 3 2 4 6 5 1 6 2 3 4 5
71. (**) Viết chương trình con xóa những phần tử sao cho mảng kết quả có thứ tự tăng dần và số lần xóa là ít nhất.
72. Cho dãy a gồm n số nguyên có thứ tự tăng dần. Nhập vào 1 phần tử nguyên X, viết chương trình con chèn X vào dãy số sao cho dãy vẫn có thứ tự tăng dần (không sắp xếp).
73. Viết chương trình tìm số lẻ nhỏ nhất lớn hơn mọi số chẵn có trong mảng.
74. Viết chương trình con tìm giá trị chẵn nhỏ nhất nhỏ hơn mọi giá trị lẻ trong mảng các số nguyên.
75. Viết chương trình con tìm phần tử xuất hiện nhiều nhất trong mảng các số nguyên.
76. Viết chương trình đếm và liệt kê các mảng con tăng dần trong mảng một chiều các số nguyên.
Ví dụ: 6 5 3 2 3 4 2 7 các dãy con tăng dần là 2 3 4 và 2 7.
77. Viết chương trình tìm mảng con tăng dần có tổng lớn nhất trong mảng một chiều.
78. (*) Viết chương trình nhập vào 1 dãy số a gồm n số nguyên (n 100). Tìm và in ra dãy con tăng dài nhất.
Ví dụ: Nhập dãy a: 1 2 3 6 4 7 8 4 5 6 7 8 9 4 5
Dãy con tăng dần dài nhất: 4 5 6 7 8 9
79. (**) Viết chương trình tách 1 mảng các số nguyên thành 2 mảng a và b, sao cho kết quả thu được là:
 Mảng a chứa toàn bộ số lẻ tăng dần.
 Mảng b chứa toàn số chẵn giảm dần.
(không dùng sắp xếp).
Hướng dẫn: Tìm vị trí chèn thích hợp khi trích phần tử mảng ban đầu.
Ví dụ: Mảng ban đầu: 9 3 8 2 7 5 1 0 10
Mảng a: 1 3 5 7 9
Mảng b: 10 8 2
80. (**) Viết chương trình in ra tam giác Pascal (dùng mảng một chiều).
81. Viết chương trình nhập vào dãy số a gồm n số thực (n 100), nhập vào dãy số b gồm m số thực (m 100).
 Hãy sắp xếp hai dãy số theo thứ tự tăng dần.
 (*) Trộn 2 dãy trên thành dãy c sao cho dãy c vẫn có thứ tự tăng.
 Xuất dãy a, b, c ra màn hình.
82. (*) Cho mảng C có n phần tử (n <200), các phần tử là các chữ số trong hệ đếm cơ số 16 (Hexa) (điều kiện mỗi phần tử 0). Liệt kê tất cả các số nguyên tố nhỏ hơn n.
5. Nhập số nguyên dương n (n>0). Liệt kê n số chính phương đầu tiên.
6. Nhập số nguyên dương n (n>0). Đếm xem có bao nhiêu số hoàn thiện nhỏ hơn n.
7. Nhập số nguyên dương n (0<= n <100) và in ra cách đọc của n.
Ví dụ: Nhập n= 105. In ra màn hình: Mot tram le nam.
8. Viết chương trình tính tiền thuê máy dịch vụ internet và in ra màn hình kết quả. Với dữ liệu nhập vào là giờ bắt đầu thuê (GBD), giờ kết thúc thuê (GKT), số máy thuê (Somay).
 Điều kiện cho dữ liệu nhập: 6<= GBD< GKT<=21. Giờ là số nguyên.
 Đơn giá: 2500đ cho mỗi giờ máy trước 17:30 và 3000đ cho mỗi giờ máy sau 17:30.
9. Viết chương trình tính tiền lương ngày cho công nhân, cho biết trước giờ vào ca, giờ ra ca của mỗi người.
Giả sử rằng:
 Tiền trả cho mỗi giờ trước 12 giờ là 6000đ và sau 12 giờ là 7500đ.
 Giờ vào ca sớm nhất là 6h sáng và giờ ra ca trễ nhất là 18h (giả sử giờ nhập vào nguyên).
10. Nhập vào 2 số nguyên p, q và tính biểu thức sau:
(-q\2+(p3\27+q2\4)1\2)1\3 +( -q\2-(p3\27+q2\4)1\2)1\3
11. Nhập vào 3 số thực a, b, c và kiểm tra xem chúng có thành lập thành 3 cạnh của 1 tam giác hay không? Nếu có hãy tính diện tích, chiều dài mỗi đường cao của tam giác và in kết quả ra màn hình.
 Công thức tính diện tích s =sqrt(p*(p-a)*(p-b)*(p-c))
 Công thức tính các đường cao: ha=2s\a, hb=2s\b, hc=2s\c.
(với p là nửa chu vi của tam giác).
12. Nhập vào 6 số thực a, b, c, d, e, f. Giải hệ phương trình sau:

13. Viết chương trình nhập 2 số nguyên dương a, b. Tìm USCLN và BSCNN của 2 số nguyên đó.
14. Viết chương trình tính tổng nghịch đảo của n giai thừa.
15. Cho 2 số nguyên a, b. Viết chương trình con hoán vị giá trị 2 số trên.
16. (*) Viết chương trình nhập số nguyên dương gồm 5 chữ số, kiểm tra xem các chữ số n có phải là đối xứng hay không.
Ví dụ: Đối xứng: 13531
Không đối xứng 13921
17. Viết chương trình nhập số nguyên dương n gồm k chữ số (0< k 5), đếm xem n có bao nhiêu chữ số chẵn và bao nhiêu chữ số lẻ.
18. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), đếm xem n có bao nhiêu chữ số là số nguyên tố.
19. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), tính tổng các ước số dương của n.
Ví dụ: Nhập n=6
Tổng các ước số từ 1 đến n: 1+2+3+6=12
20. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), tìm ước số lẻ lớn nhất của n.
Ví dụ: Ước số lẻ lớn nhất của 27 là 9.
21. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), kiểm tra xem các chữ số của n có toàn lẻ hay toàn chẵn không.
22. (*) Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), sắp xếp các chữ số của n theo thứ tự tăng dần.
Ví dụ: Nhập n = 1536
Kết quả sau khi sắp xếp: 1356.
23. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), sau đó nhập một số nguyên x, tìm vị trí xuất hiện của chữ số có giá trị x trong n.
Ví dụ: Nhập n = 1526, x=2
Kết quả: Chu so 2 o vi tri thu 3.
24. Viết chương trình nhập số nguyên dương n gồm k chữ số(0< k 5), kiểm tra xem các chữ số của n có được sắp thứ tự không.
Ví dụ: Nhập n = 1569 hoặc n =8521
Kết quả: Có thứ tự.
25. Viết chương trình nhập 2 số a, b sao cho: số lớn nhất trong 2 số phải là một số dương và chia hết cho 7. Nếu nhập sai phải yêu cầu nhập lại cho đến khi đúng.
26. Viết chương trình nhập số nguyên dương n gồm k chữ số (0< k 5), tính giá trị trung bình các chữ số chẵn trong n.
27. (*) Viết chương trình in ra màn hình ngày/tháng /năm của ngày hiện tại, cho phép sử dụng các phím mũi tên lên, xuống để tăng hoặc giảm 1 ngày.
28. (*) Viết chương trình in ra màn hình giờ : phút : giây hiện tại, cho phép sử dụng các phím mũi tên lên, xuống để tăng hoặc giảm một giây.

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