Session Library for CodeIgniter using PHP native session

<?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
*/
class CI_Session {
    var $session_id_ttl = 360; // session id time to live (TTL) in seconds
    var $flash_key = 'flash'; // prefix for "flash" variables (eg. flash:new:message)

    function __construct()
    {
        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();
    }

    /**
    * 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)
            {
                $_SESSION[$key] = null;
                unset($_SESSION[$key]);
            }
        }
    }

    /**
    * Starts up the session system for current request
    */
    function _sess_run()
    {
        session_start();

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

		if (count($newdata) > 0)
		{
			foreach ($newdata as $key => $val)
			{
				$flashdata_key = $this->flash_key.':new:'.$key;
				$this->set_userdata($flashdata_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);
            }
        }
    }

    /**
	 * Fetch all session data
	 *
	 * @access	public
	 * @return	array
	 */
	function all_userdata()
	{
		return $_SESSION;
	}

	/**
	 * Destroy the current session
	 *
	 * @access	public
	 * @return	void
	 */
	function sess_destroy()
	{
		$this->destroy();
	}


}

/* EOF */