Every medium (or larger) application needs a bit of configuration variables, the only questions are the scale and the desire of the developer to spend more than a minute building it.
So lets make it quick.
I'm going to show 3 basic concepts of wide-system configuration storage with PHP.
Method 1: Plain PHP Array
This maybe the most simple and efficient method of all. Just keep your configurations inside a PHP array and use it globally across your app. Simple to use, fast to develop.