PHP is mainly focussed on server side scripting so that you can do anything any other CGI language can do.
There are three widely areas in which PHP is used
1. Server side scripting : PHP is server side scripting language in which the processing is done at the server end and response transferred as HTML and presented to the user.
2. Command Line Scripting : One does not requires borwser or server to run a php script. You only need the PHP parser to use it this way. This type of usage is ideal for scripts regularly executed using cron.
3. Writing desktop applications : PHP can be used to write desktop application by using PHP-GTK to write such programs.
PHP is platform independent and can be run on any modern web server. Beside this, PHP has the support to write both procedural as well as object oriented programming(OOPS) or mixture of both.