session timeout?

How can I make my site auto log out a user like I've seen on many sites? Right now, the users session never expires unless manually logging out or the browser is closed. Also, should I change anything to cover any security issues? I havn't changed much from the default, only enough to get it running for my site. Here is what I have in my php.ini file: [Session] session.save_handler = files session.save_path = /var/www/sessions session.use_cookies = 1 session.name = NittanyTravelSessionCookie session.auto_start = 0 session.cookie_lifetime = 0 session.cookie_path = / session.cookie_domain = session.serialize_handler = php session.gc_probability = 1 session.gc_maxlifetime = 1440 session.referer_check = session.entropy_length = 0 session.entropy_file = ;session.entropy_length = 16 ;session.entropy_file = /dev/urandom session.cache_limiter = nocache session.cache_expire = 180 session.use_trans_sid = 1 url_rewriter.tags = "a=href,area=href,frame=src,input=src,form=fakeentry" Thanks, Jake