General Introduction

PHP is a server scripting language, and is a powerful tool for making dynamic and interactive Web pages.

PHP stands for PHP: Hypertext Preprocessor.It is a widely-used, open source scripting language.
Its scripts are executed on the server. It is free to download and use.

To start using PHP, we have:
 install a web server
 a web host with PHP and MySQL support.
Install a web server on your own PC, and then install PHP and MySQL

A PHP script can be placed anywhere in the document.
A PHP script starts with <?php and ends with ?>:

<?php
// PHP code goes here
?>

 The default file extension for PHP files is ".php".

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.