Native Session for CodeIgniter 2

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

/**
* Code Igniter
*
* An open source application development framework for PHP 4.3.2 or newer
*
* @package     CodeIgniter
* @author      Dariusz Debowczyk
* @copyright   Copyright (c) 2006, D.Debowczyk
* @license     http://www.codeignitor.com/user_guide/license.html
* @link        http://www.codeigniter.com
* @since       Version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* Session class using native PHP session features and hardened against session fixation.
*
* @package     CodeIgniter
* @subpackage  Libraries
* @category    Sessions
* @author      Dariusz Debowczyk
* @link        http://www.codeigniter.com/user_guide/libraries/sessions.html
*/
/**
* Adjusted some function for CodeIgniter 2
* @package     CodeIgniter
* @subpackage  Libraries
* @category    Sessions
* @author      kakilangit
*/
class CI_Session {
  var $flash_key = 'flash';// prefix for "flash" variables (eg. flash:new:message)
  function __construct(){
    $this->object =& get_instance();
    log_message('debug', 'Native_session Class Initialized');
    $this->_sess_run();
  }

  /**
    * Regenerates session id
    */
  function regenerate_id(){// copy old session data, including its id
    $old_session_id = session_id();
    $old_session_data = $_SESSION;// regenerate session id and store it
    session_regenerate_id();
    $new_session_id = session_id();// switch to the old session and destroy its storage
    session_id($old_session_id);
    session_destroy();// switch back to the new session id and send the cookie
    session_id($new_session_id);
    session_start();// restore the old session data into the new session
    $_SESSION = $old_session_data;// update the session creation time
    $_SESSION['regenerated'] = time();// session_write_close() patch based on this thread
    // http://www.codeigniter.com/forums/viewthread/1624/
    // there is a question mark ?? as to side affects
    // end the current session and store session data.
    session_write_close();
  }

  /**
    * Destroys the session and erases session storage
    */
  function destroy(){
    unset($_SESSION);

    if (isset($_COOKIE['session_name()'] ) )
    {
      setcookie(session_name(), '', time()-42000, '/');
    }

    session_destroy();
  }

  function sess_destroy(){
    $this->destroy();
  }

  /**
    * Reads given session attribute value
    */
  function userdata($item){

    if ($item == 'session_id')
    {//added for backward-compatibility
      return session_id();
    }
    else
    {
      return(! isset($_SESSION[$item])) ? false : $_SESSION[$item];
    }
  }

  /**
    * Sets session attributes to the given values
    */
  function set_userdata($newdata = array(), $newval = ''){

    if (is_string($newdata))
    {
      $newdata = array($newdata => $newval);
    }


    if (count($newdata) > 0)
    {

      foreach ($newdata as $key => $val)
      {
        $_SESSION[$key] = $val;
      }
    }
  }

  /**
    * Erases given session attributes
    */
  function unset_userdata($newdata = array()){

    if (is_string($newdata))
    {
      $newdata = array($newdata => '');
    }


    if (count($newdata) > 0)
    {

      foreach ($newdata as $key => $val)
      {
        unset($_SESSION[$key]);
      }
    }
  }

  /**
    * Starts up the session system for current request
    */
  function _sess_run(){
    session_start();
    $session_id_ttl = $this->object->config->item('sess_expiration');

    if (is_numeric($session_id_ttl))
    {

      if ($session_id_ttl > 0)
      {
        $this->session_id_ttl = $this->object->config->item('sess_expiration');
      }
      else
      {
        $this->session_id_ttl = (60*60*24*365*2);
      }
    }

    // check if session id needs regeneration

    if ($this->_session_id_expired() )
    {// regenerate session id (session data stays the
      // same, but old session storage is destroyed)
      $this->regenerate_id();
    }

    // delete old flashdata (from last request)
    $this->_flashdata_sweep();// mark all new flashdata as old (data will be deleted before next request)
    $this->_flashdata_mark();
  }

  /**
    * Checks if session has expired
    */
  function _session_id_expired(){

    if (!isset($_SESSION['regenerated'] ) )
    {
      $_SESSION['regenerated'] = time();
      return false;
    }

    $expiry_time = time() - $this->session_id_ttl;

    if ($_SESSION['regenerated'] <= $expiry_time )
    {
      return true;
    }

    return false;
  }

  /**
    * Sets "flash" data which will be available only in next request (then it will
    * be deleted from session). You can use it to implement "Save succeeded" messages
    * after redirect.
    */
  function set_flashdata($newdata, $newval='') {

    if (is_string($newdata))
    {
      $newdata = array($newdata => $newval);
    }


    if (count($newdata) > 0)
    {

      foreach ($newdata as $key => $val)
      {
        $flash_key = $this->flash_key.':new:'.$key;
        $this->set_userdata($flash_key, $val);
      }
    }
  }

  /**
    * Keeps existing "flash" data available to next request.
    */
  function keep_flashdata($key){
    $old_flash_key = $this->flash_key.':old:'.$key;
    $value = $this->userdata($old_flash_key);
    $new_flash_key = $this->flash_key.':new:'.$key;
    $this->set_userdata($new_flash_key, $value);
  }

  /**
    * Returns "flash" data for the given key.
    */
  function flashdata($key){
    $flash_key = $this->flash_key.':old:'.$key;
    return $this->userdata($flash_key);
  }

  /**
    * PRIVATE: Internal method - marks "flash" session attributes as 'old'
    */
  function _flashdata_mark(){

    foreach ($_SESSION as $name => $value)
    {
      $parts = explode(':new:', $name);

      if (is_array($parts) && count($parts) == 2)
      {
        $new_name = $this->flash_key.':old:'.$parts[1];
        $this->set_userdata($new_name, $value);
        $this->unset_userdata($name);
      }
    }
  }

  /**
    * PRIVATE: Internal method - removes "flash" session marked as 'old'
    */
  function _flashdata_sweep(){

    foreach ($_SESSION as $name => $value)
    {
      $parts = explode(':old:', $name);

      if (is_array($parts) && count($parts) == 2 && $parts[0] == $this->flash_key)
      {
        $this->unset_userdata($name);
      }
    }
  }
}
?>