class Welcome extends CI_Controller {
 public function __construct()
 {
  parent::__construct();
  
  session_start();
 }
 
 public function index()
 {
  $_SESSION['test'] = 'test';

  $this->load->view('welcome_message');
 }
 
 public function sess_test()
 {
  echo $_SESSION['test'];
 }
}