Strange error in custom library

[eluser]Razican[/eluser]
Yes, that was the problem, but I get another error.

Is it possible to know the online users with the session class? doing this?

Code:

function online()
    {
        $query                = $this->db->get('sessions');

        return $query->num_rows();
    }

I mean, does the session class delete sessions from the database after $config['sess_time_to_update'] has gone? or it deletes them after $config['sess_expiration']?

It would be easier for me that way. I only want to know how many people has the last activity later than time()-$config['sess_time_to_update'].