Allow php sessions to carry over to subdomains

Question

I use php sessions (not cookies, except for session id cookie) for all user data, and when a user goes to their profile user.mydomain.com they are immediately \"logged out\"

Answer 1

I just had this problem and it turns out I was using different php.ini files for two different sub-domains. These ini files specified different session.save_path variables. For obvious reasons this needs to be the same for all sub-domains that need to share sessions.