Codeigniter - check if user is logged and exists (it's a real user)

Question

I'm trying to set session data for users when they log in to my website.

So if the user exists in db, I set a session data like : $this->session->set_userdata('user_exists','1');

Now every time i want to check if user exists and is logged i do:

if($this->session->userdata('user_exists')){
 //do somenthing for logged user
}

Now I'm wondering if this means that user is logged and exists in the database since he logged and I set him a session param, is this true? Or I'll get security problems?

NB: I'm using session database

Solution

//session encryption is mandatory

  $sess_id = $this->session->userdata('user_id');

   if(!empty($sess_id))
   {
        redirect(site_url().'/reports');

   }else{

        $this->session->set_userdata(array('msg'=>'')); 
        //load the login page
        $this->load->view('login/index');        
   }