PHP is a server-side scripting language that enables you develop dynamic websites quickly.
PHP has become one of the most popular server-side scripting languages on the web. The fact that it's free can only help its popularity. Using PHP, you can do all sorts of things such as query a database, send email newsletters, upload files to the server, and much more.
This PHP Tutorial covers the fundamentals of PHP programming, and demonstrates just how easy it is to create dynamic websites using PHP.