One week the session open to expire is secure

I cant remember where I learned it, but I use:

PHP Code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Myclass extends CI_Controller
{
    private $logged_in; 


then in the construct

PHP Code:

$this->logged_in = ($this->session->userdata('signed_in')) ? TRUE : FALSE; 


So, as soon as user is logged in, I set a sessiondatapiece signed_in = 1