[thelist] PHP session lifetime?!

[Eduardo Bacchi Kienetz]

Hey guys, here is my problem:
I've made a login system using sessions with PHP (session_register ...
session_start). That works ok. The problem is that when I type in some
other web address and go to that page, if I use the Back button, then the
browser says the page expired.
Would I have to start using cookies (I didn't want it because I'm gonna
have to make functions to check, etc, and some browsers don't support
cookies or may even have it disabled) ?
Isn't there a variable that I can set which defines the expiring time of
the session?

Thank you in advance,

Eduardo Bacchi Kienetz
Santa Maria - RS - Brazil