increase php session times

Hi.

i am working on project which is hosted on opensuse system but i am working on it using win xp machine.
on my local system i remain logged in till i logout but on actual project my session gets ended after approx 30 min.
i checked session settings in my winxp and suse php.ini files and regarding session settings they are same.

where should i look next?
thanks

http://php.net/manual/en/session.configuration.php

Thanks MattF

i checked that page and i think i need to increase
setting session.gc_maxlifetime from 1440 to 86400