1 What is PHP?

　PHP ("PHP: Hypertext Preprocessor", abbreviation of Hypertext Preprocessor) is a widely used open source multi-purpose scripting language. It can be embedded into HTML and is especially suitable for web development.

2 What can PHP do?

PHP scripts are mainly used in the following three areas:
Websites and web applications (server-side scripting). You need the following three things: PHP parser (CGI or server module), web server and web browser.
Command line script. You can write a PHP script and don't need any server or browser to run it. Just requires a PHP parser to execute.
Desktop (GUI) application. These programs can be written using PHP-GTK. PHP-GTK is an extension of PHP that is not included in the commonly distributed PHP packages.