Like Garthor said, it checks to see if the client is in the subscription list, if it is return TRUE, if not return FALSE. But, if it's giving them some type of stat boost of some sort, be sure to put a variable in there to identify if they had already gotten the boost. And, if it's for a fangame, you legally can't charge for anything related to the game (in ex: "SSJ999" or, "Goku's SUPER-DUPER EXTRA HEAVY PEN!")