How do I delete the Facebook user cookie? [closed]

Question

If I logout in my application the user is logged out in my application but not in Facebook.

When I login again via Facebook the same user cookies are used to login again - I need a different user to login after I logout.

The following logout function is used in my application:

 public function logout()
        { 
        session_destroy();

        $this->session->sess_destroy();

        $this->facebook->destroySession();  

        if ($this->facebook_user)
        { 

        $this->facebook->destroySession();  


        $logoutUrl = $this->facebook->getLogoutUrl(); 

        redirect($logoutUrl);   
        }



        redirect('con_home');   
    }