php Sentry: Force user to logout

Question

I want to automatically logout inactive users. Problem is that users are still logged when I mark them as inactive.

I think that problem is that session variable for each inactive user are still valid and they can easily login even if I mark them as they are not online.

Does someone knows where's the problem ?

DB::table ( 'users' )->where ( 'username', $user->username )->update ( array (
                                'online' => 0,
                                'kicked' => '' 
                        ) );