PHP is the most frequently used server-side programming language on webservers today and can be used to generate dynamic content, most commonly by interacting with a database, such as MySQL. Many server-side applications such as blogs, forums and content management systems are written in PHP with MySQL database support. PHP is also used for a wide variety of server-side applications ranging from form processing to image resizing.

More information about PHP can be found at http://www.php.net/