Only if they've got two browser windows open, the session has a lifetime of zero, which is the default, but can be set with... wait for it [man]session_set_cookie_params[/man] and one final thing - the browser isn't firefox, because as lovely as it is it always carries a session between tabs/windows everything - and this caused me a massive headache and rewrite of some software I should have done 'properly' in the first place.