PHP: Session not working

when user log's in at client, i am redirecting to server, ther i am setting session on user_id once his user_id and password are verified, i am redirecting back to client. then, i am asking to fill profile info. if he want to fill the info by facebook, popup window appear which asks for permision to facebook api.

then i want to store access token into db. for this i am redirecting to server with user_id , accesstoken and other info to server. there i am checking session to verify that he is same user.

but not working. more details:

In server, i have two function, validate() and facebook(). In validate function, i am creating session. when i am going from validate function to facebook function and thr if if i echo session of 'user_id' it is printing. -------- but, when i go validate function to client site and then if came back to server/facebook it is not pri开发者_StackOverflow社区nting

Did you use the function session_start() ?

That will fix the problem most of the times.