Facebook Login + Registration

I have looked through dev docs and and tutorials via google engine, but I am kinda lost plus I am no expert in logic or programming..

I am trying to combine with login and register on the page. If user have fb account, they can log in. and then have database store their information for shopping purpose. if not, they could register and again have database store their info.

How to combine them using PHP SDK? Also I notice that I couldn't use Javascript SDK for login and register (do I need to crea开发者_运维百科te two apps for login and register?)

Insight will be appreciated. thank you very much

If you are talking about the "Registration Plugin" then I've written a tutorial about this:
How To: Use Facebook Registration Plugin As Your Registration System