Sessions disappearing?

[eluser]@li[/eluser]
Hi, I'm using the CodeIgniter session library, storing the sessions to the database.

I have a strange problem, whenever I set a session and redirect a user, using:

Code:

$this->session->set_userdata('foo', 'bar');

I'm able to access this variable just fine the first time around, but if I do a page refresh this session value is gone.. what's the reason behind this?

Edit: It seems that in config.php, changing this:

Code:

$config['sess_expiration']        = 7200;

to this:

Code:

$config['sess_expiration']        = 0;

fixes this issue, even though if the variable is set to 7200, that should mean that the session would be active for 7200 seconds (i.e 2 hours) while it actually disappears with each page load.