CodeIgniter的Session问题

最近有个项目接触到CodeIgniter,让我很是惊叹它的精巧，于是决定用它来做下一个项目。果然，蜜月期过了，毛病就出来了，具体的就是Session的问题。CodeIgniter的Session有两种方式，默认的Session是用Cookie来存储的，也可以切换到数据库存储，但是无论哪种Session都会有些很致命的问题，就是丢失数据。

比如 Controller a.php

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

class A extends CI_Controller {
    function __construct()
    {
        parent::__construct();
    }
    function index()
    {
        $this->load->view('a');
    }
    function test()
    {
        $user_data=array();
        $user_data['testval']=$this->input->post('testval');
        $this->session->set_userdata($user_data);
        redirect('b','refresh');
    }
}
?>

Controller B:

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

class B extends CI_Controller {
    fucntion __construct()
    {
        parent::__construct();
    }
    function index()
    {
        echo('#'. $this->session->userdata('testval') . '#');
        $this->load->view('a');
    }
}
?>

View A:

<hr/>
<form action="A/test" method="post">
<input type="text" name="testval" id="testval" value="1234" />
<input type="submit" value="submit"/>
</form>

在autoload.php里面修改，加上对 Session的load

$autoload['libraries']=array('database','session');

然后访问 A， 比如  http://localhost/A, 点提交之后应该刷新，在刷新后的页面上显示出来 1234， 然后神奇的事情发生了。。。 Session没了， 对于redirect, CodeIgniter自动的创建了一个新的session，同样的道理，如果用Ajax访问，也会有个新的Session被创立，结果导致了这个Session根本不能用！

折腾了整整一天也没什么效果，后来在github上面找到了一个大牛自己改写的Session Library, 核心就是弃用cookie，转而使用php native session， 保留了一些基本功能，比如 set_userdata()，这需要用下面的代码 覆盖 system/libraries/Session.php 文件

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

   // function Native_session()
    function CI_Session()
    {
        $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();
    }

    /**
    * 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_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);
            }
        }
        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($key, $value)
    {
        $flash_key = $this->flash_key.':new:'.$key;
        $this->set_userdata($flash_key, $value);
    }

    /**
    * 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);
            }
        }
    }
}
?>

问题解决了，但是也有局限，

第一 $this->session->sess_create() 和$this->session->sess_destroy() 不见了, 这倒无所谓，没太大影响， 可以用 $this->session->destroy(),

第二，这修改了CodeIgniter的system library，并不是特别好的解决方法。。。

哎～ 不过不管怎么说，解决了， 浪费了整整1天的时间。。。

点击这里下载Session.php ,修改自 https://github.com/EllisLab/CodeIgniter/wiki/Native-session