PHP is a programming language widely used on the web. It’s chief strengths are the fact that it can be embedded into HTML pages and run automatically by the server - unlike Perl and Python it doesn’t have to be stored in hidden CGI folders. That may also be a security liability, however, even though it’s more convenient for the webmaster.

PHP is very much like C, so it’s easy to learn.

To run PHP on your home computer you’ll need to be running a web server. That makes it a poor language choice for home scripting. OS X comes with Perl, Python, and Ruby, not to mention Applescript, all of which would be better choices for writing scripts on your desktop.