First, I'd like to say this isn't a general question on the Facebook php/javascript sdk. I've successfully added the "Facebook login button" to a few little test projects.

My question is, what is the best way to show the user is *wanting* to log in with Facebook. Just because someone is logged in to Facebook when the visit my site, doesn't necessarily mean they want to login to my site *with* Facebook.

I know that after authorizing the user with a FB app, it redirects with a variety of `$_GET` variables, but if my user is returning to my site, and has already authorized my app, how can I create a "Facebook Login" button that basically 'says' `If user clicks this button, pull Facebook user_profile, and use their info for login, else require Facebook login as normal`.

I know I could create a button, forward to a page, set a session var, and redirect to the main page, but I'd like to create this effect without noticeable redirections; no redirections if possible.