Codeigniter ประยุกต์ใช้ Hooks กับการทำ User Online

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
$hook['post_controller'] = array(
	'class'    => 'User_online',
	'function' => 'online',
	'filename' => 'User_online.php',
	'filepath' => 'hooks',
	'params' => ''
);
/*
pre_system ถูกเรียกตั้งแต่แรกเริ่มของการทำงานระบบ
pre_controller ถูกเรียกทันทีก่อนที่ตัวควบคุม (controller) ใดๆจะถูกเรียก
post_controller_constructor ถูกเรียกทันทีเมื่อ constructructor ทำงาน
post_controller ถูกเรียกทันทีเมื่อ controller ทำงานเสร็จสมบรูณ์
*/

/* End of file hooks.php */
/* Location: ./application/config/hooks.php */

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

class User_online
{
	var $CI;
	function __construct()
    {
		$this->CI = & get_instance();
    }
	function online()
	{
		$timeoutseconds = 300;
		$timeout = time() - $timeoutseconds;
		$this->CI->db->query("DELETE FROM users_online WHERE last_activity < ".$timeout);
		$data = $this->CI->session->all_userdata();
		if (isset($data['username']))
		{
			$this->insert_data($data);
		}
	}
	function insert_data($data)
	{
		$array = array(
		   'uid' => $data['user_id'] ,
		   'username' => $data['username'] ,
		   'ip_address' => $data['ip_address'] ,
		   'session_id' => $data['session_id'] ,
		   'user_agent' => $data['user_agent'] ,
		   'last_activity' => time(),
			'uri' => $_SERVER['REQUEST_URI']
		);
		$count = $this->CI->db->where('uid', $data['user_id'])->from('users_online')->count_all_results();
		if ($count === 0)
		{
			$this->CI->db->insert('users_online', $array); 
		}
		else
		{
			$this->CI->db->update('users_online', array('last_activity' => time(), 'uri' => $_SERVER['REQUEST_URI']), array('uid' => $data['user_id'])); 
		}
	}
}

/* End of file users_online.php */
/* Location: ./application/hooks/user_online.php */

CREATE TABLE IF NOT EXISTS `users_online` (
  `uid` int(11) NOT NULL,
  `username` varchar(50) NOT NULL,
  `ip_address` varchar(40) NOT NULL,
  `session_id` varchar(50) DEFAULT NULL,
  `user_agent` varchar(200) DEFAULT NULL,
  `last_activity` int(15) NOT NULL,
  `uri` varchar(250) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;