they should all ready be logged in from facebook cause they have to like the page if you follow what i mean
So you just want it to be a like button deal? http://developers.facebook.com/docs/reference/plugins/like http://developers.facebook.com/docs/opengraph those should show you how to do it without even having to add any php at all. for sign up / regstrations http://developers.facebook.com/docs/guides/web by default you cant store there user info from facebook on your site, I'm not sure if its a REST, SOAP, or JSON service for the login service. You only get a session returned to you, theres an example of how to do it as well. I hope that is more helpful to you then I was able to be.
