PHP is a general-purpose language whose main function is for the development of dynamic websites that access databases.
Ever since it first appeared, PHP has been one of the most versatile and stable script languages for creating websites on Linux or even Windows servers. PHP perfectly integrates with MySQL databases and Apache servers.
The PHP syntax is very similar to the programming language C, so if you are already familiar with the latter you won't have any problems getting used to PHP.
Also, PHP is a very well documented language that has a limitless supply of resources. Go to http://www.php.net/, where you can find a large quantity of help files for PHP.
