php sessions

Hi! I have a few questions about the sessions in php. I have a website where users are authentified through a login/password stored in a database. Once accepted, I start a session. - can I "disconnect" an user? I mean I have a logout script, which is called when the user wants to logout, but can I log him out myself? I was thinking deleting the session files in php/tmp, but I don't have this access (and don't think it is a good way). My second idea was logging myself as this user (as I know the login/pass), but will this end its session? I am not recoding the logout in the sql tables, so is there any way for me to kno which sessions are still active? - this lead to my second question, can I limit the number of session per user (to 1)? I think it is possible, because I saw on some websites the warning "only one active session allowed per user, if you are already logged in you will be disconnected" but I don't know how this is managed. - if my user is logged in (active session) and try to re-log in, will he open a new session or will he re-use the already opened one? I think the global idea behind all this is how to attach a session to an user and how to control it. Thanks for your help! _________________________________________________________________ Want to block unwanted pop-ups? Download the free MSN Toolbar now! http://toolbar.msn.co.uk/