Is there anyway that I can make it so that if the user goes to a site outside of mine, without logging out of mine, the user's session variables are removed and the session destroyed? (I'm using cookies sessions).
Well, I guess you can set the expire date of the cookie to a reasonable time.
For example 5 minutes.
So If the user keeps browsing your site, the cookie will be updated everytime he loads a new page.
If the user don't update that cookie, it'll be removed automatically.
You can also add a loggout button, but people don't use it really...