Ending a session in php or with php when a user exits the domain?

I am working on a site and I use session variables to store some info. What I need to do is destroy the session automatically when the user leaves the domain but have forgotten how to do that.|||The session destroys automatically when the user closes his browser, I think one of the Javascript functions (can't think right now.) would be able to help a bit, but then again it is horrible for the people who have it disabled.|||Create a cookie so when they visit the site again it'll refresh the session =)|||RAM chips just deleted your file when log off.