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 (OSS)
* PHP is free to download and use

What is a PHP File?

* PHP files may 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 small database server
* MySQL is ideal for small and medium 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 (means that 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: www.php.net
* PHP is easy to learn and runs efficiently on the server side

Where to Start?

* Install an Apache server on a Windows or Linux machine
* Install PHP on a Windows or Linux machine
* Install MySQL on a Windows or Linux machine
What do You Need?

This tutorial will not explain how to install PHP, MySQL, or Apache Server.

If your server supports PHP - you don't need to do anything! You do not need to compile anything or install any extra tools - just create some .php files in your web directory - and the server will parse them for you. Most web hosts offer PHP support.

However, if your server does not support PHP, you must install PHP. Below is a link to a good tutorial from Webmonkey on how to install PHP4:

http://hotwired.lycos.com/webmonkey/00/44/...?tw=programming
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://www.php.net/manual/en/installation.php

Basic PHP Syntax

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:
Code:
html>
<body>

<?php echo "Hello World"; ?>

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

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".

Variables in PHP
All variables in PHP start with a $ sign symbol. Variables may contain strings, numbers, or arrays.

Below, the PHP script assigns the string "Hello World" to a variable called $txt:
Code:
<html>
<body>

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

</body>
</html>
To concatenate two or more variables together, use the dot (.) operator:

Code:
<html>
<body>

<?php
$txt1="Hello World";
$txt2="1234";
echo $txt1 . " " . $txt2;
?>

</body>
</html>
The output of the script above will be: "Hello World 1234".

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

Code:
<html>
<body>

<?php

//This is a comment

/*
This is
a comment
block
*/

?>

</body>
</html>
PHP Operators
This section lists the different operators used in PHP.

Arithmetic Operators
Code:
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

Code:
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
Comparison Operators
Code:
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
Code:
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
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 two conditional statements:

* if (...else) statement - use this statement if you want to execute a set of code when a condition is true (and another if the condition is not true)
* switch statement - use this statement if you want to select one of many sets of lines to execute

The If Statement
If you want to execute some code if a condition is true and another code if a condition is false, use the if....else statement.

Syntax

Code:
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!":

Code:
<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 when a condition is true, the lines should be enclosed within curly braces:
Code:
<html>
<body>

<?php
$x=10;
if ($x==10)
{
echo "Hello
"; 
echo "Good morning
";
}
?>

</body>
</html>
The Switch Statement

If you want to select one of many blocks of code to be executed, use the Switch statement.
Syntax
Code:
switch (expression)
{
case label1:
 *code to be executed if expression = label1;
 *break; *
case label2:
 *code to be executed if expression = label2;
 *break;
default:
 *code to be executed
 *if expression is different 
 *from both label1 and label2;
}
Example

This is how it works: First we have a single expression (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 none of the cases are true.

Code:
<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>
Looping statements in PHP are used to execute the same block of code a specified number of times.

Looping

Very often when you write code, you want the same block of code to run a number of times. You can use looping statements in your code to perform this.

In PHP we have the following looping statements:

* while - loops through a block of code as long as a specified condition is true
* do...while - loops through a block of code once, and then repeats the loop as long as a special 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 Statement

The while statement will execute a block of code if and as long a condition is true.
Syntax
Code:
while (condition)
code to be executed;
Example

The following example demonstrates a loop that will continue to run as long as the variable i is less than, or equal to 5. i will increase by 1 each time the loop runs:
Code:
<html>
<body>

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

</body>
</html>
The do...while Statement

The do...while statement will execute a block of code at least once - it then will repeat the loop as long as a condition is true.
Syntax

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

The following example will increment the value of i at least once, and it will continue incrementing the variable i while it has a value of less than 5:
Code:
<html>
<body>

<?php 
$i=0;
do
{
$i++;
echo "The number is " . $i . "
";
}
while ($i<5);
?>

</body>
</html>
The for Statement

The for statement is used when you know how many times you want to execute a statement or a list of statements.
Syntax
Code:
for (initialization; condition; increment)
{
 * *code to be executed;
}
Note: The for statement has three parameters. The first parameter is for initializing variables, the second parameter holds the condition, and the third parameter contains any increments required to implement the loop. If more than one variable is included in either the initialization or the increment section, then they should be separated by commas. The condition must evaluate to true or false.
Example

The following example prints the text "Hello World!" five times:
Code:
<html>
<body>

<?php
for ($i=1; $i<=5; $i++)
{
echo "Hello World!
";
}
?>

</body>
</html>
The foreach Statement

Loops over the array given by the parameter. On each loop, the value of the current element is assigned to $value and the array pointer is advanced by one - so on the next loop, you&#39;ll be looking at the next element.
Syntax
Code:
foreach (array as value)
{
 * *code to be executed;
}
Example

The following example demonstrates a loop that will print the values of the given array:
Code:
<html>
<body>

<?php
$arr=array("one", "two", "three");
foreach ($arr as $value)
{
echo "Value: " . $value . "
";
}
?>

</body>
</html>


Source= W3 Schools- www.w3schools.com