How can i kick first Logged user?

[eluser]slowgary[/eluser]
I'm pretty sure it's possible that the user's IP address could change mid-session. Some proxies do this, probably most commonly at universities. You might want to check a combination of fields to determine whether it's the same user or not, including the user agent.

You could just skip the check altogether and kick them out upon an attempt to login. I think that's what Dam1an was getting at. So if a user is already logged in and attempts to login again, you'd destroy the first session. This method would require you to hide login forms from logged in users.