When a user logins I get him/her\'s ID and save it in a session var. What I wonder is, is this the way to go? Or should I use cookies? so it automatically login and so on.
Cookies can be manipulated very easily. Manage login/logout with Sessions. If you want, you can store the users emailaddress/username in a cookie, and fill the username box for them the next time they visit after the present session has expired.