Scripts written in PHP will almost always run on any PHP-enabled webserver with no tweaking. The most common server on a Unix-based server is Apache, which is used by the majority of web servers around the world. Apache alone does not provide PHP support, so you must download a PHP module that can be dynamically loaded by Apache:
http://www.php.net/downloads.php

You'll almost certainly need MySQL if your PHP script uses a database system:
http://mysql.org/downloads/

Once you've installed all this, you'll probably find that your script runs easily.

Hope this helps