How t increase session timeout

[chaitanyajakhad]

Hello,
How to increase session timeout if we do not have access to php.ini.

ini_set('session.cookie_lifetime','10800');
ini_set('session.gc_maxlifetime','10800');
ini_set('session_cache_expire','10800');

I tried above one but, using ini_set function we can decrease timeout, but how to increase timeout?

Regards,

Chaitanya Jakhadi.