Forcing a new Session ID?

Im trying to implement some security routines with the Session ID processing so if someone tries hijacking someone else's session based on certain variables that fail then they will be forced to get a new session id. Ive been trying to figure this out, but have had no luck. What would be the best way to do this -without- destroying the existing user's session. I tried stuff like: $newsid = md5(rand); session_name($newsid); -or- session_id($newsid); Neither one seems to have any change or affects the session id. Suggestions, ideas, etc would be appreciated. Thanks! Jon Mitchiner ICQ # 21030881 AIM # MinotaurT