How do I use HttpService to my advantage?

github.com/Voiliax/RbxPHP/blob/master/change-rank.php

The following link I posted is a PHP script meant to change the rank of a player ingame, with the assistance of a server. It's a PHP script that allows you to automatically change rank of users in a group in-game with HttpService. I am a newbie at PHP scripts but I really want to set this up to be like a gui command in which a player can be ranked up. Can someone help put together some type of lua code to make the PHP script useful? Also how/ where do I store the PHP script?