CI(5) session管理

<?php
class sess extends CI_Controller
{
public function __construct()
{
parent::__construct();
$this->load->library('session');
}
public function index()
{
if($this->session->userdata('login'))
{
echo '已经登陆';
}
else
{
echo '尚未登陆';
}
}
public function login()
{
$this->session->set_userdata(array('login'=>'蜘蛛侠'));
}
public function loginout()
{
$this->session->unset_userdata('login');
}
}
?>