为什么PHP会话信息不能通过浏览器重启持续存在，即使cookie和PHPSESSID仍然存在？

Question

Logins on a PHP site I am working on are managed by session cookies which store the userid in the session. This works fine until the browser is closed, at which point the userid information seems to be being lost.

I've set the gc and the cookie keepalive time each to seven days, and the php session settings are as follows (set via .htaccess):

session.use_cookies On  On
session.cookie_lifetime 604800  0
session.gc_divisor  1000    1000
session.gc_maxlifetime  604800  1440
session.gc_probability  0   0

I can verify with Chrome and Firebug that PHPSESSID does have a lifetime of seven days and that it is persisting between browser restarts. However, session variables such as the userid are definitely not being preserved (I can use var_dump on a separate page to verify this). What could be causing session variables to be deleted between browser restarts, if gc and cookie lifetimes are being set properly?

Answer 1

The problem ended up being with the hosting provider, Rackspace Cloud. Rackspace Cloud Sites saves $_SESSION information per-server by default but does not attempt to direct the same user to the same server between browser restarts. I'll have to set up a database-based session system or store the session files somewhere else.

My question might have been unclear because of the conflict between "session cookie" (a cookie that only lasts until browser restart) and the $_SESSION information which is supposed to persist until garbage collection.