Based on user id, determine if a user is an app user for your app (php, not fbml!)

I know of the FBML tag to see if "is app user" for an id, but how can I determine that w开发者_JS百科ithin PHP itself?

It seems that i have misread the question. if you want to know if your user is an app user or not you cannot use the graph api.

When a user comes to your application for the first time facebook sends you some data regarding that user. At that time you can decide what to do with that information. An easy way would be to use a database and store the id of that user so you can later use it when you want to check if other users have used your app or not.