sql server-PHP:自定义会话处理程序不序列化在Windows上不工作

我的应用程序的开发环境是Zend Framework 1.11、MSSQL Server 2012、用于与PDO数据库连接的SQLRV扩展、Windows 7、IIS 7。使用自定义会话处理程序类将会话存储在数据库中。

问题是，当我在Bootstrap.php文件中写入的SESSION_start（）之后打印$_SESSION时，它不会显示完整的未序列化的会话数据数组。似乎会话数据是由会话类处理程序的"读取"方法返回的，但由于某种原因没有未进行序列化。这是我的源代码：-

引导程序.php

protected function _initSession() {
    $handler = new Mcd_Core_SessionHandler_Database();
    session_set_save_handler(
        array($handler, 'open'),
        array($handler, 'close'),
        array($handler, 'read'),
        array($handler, 'write'),
        array($handler, 'destroy'),
        array($handler, 'gc')
    );        
    session_start();
    echo "<pre>";
    print_r($_SESSION);
}

会话处理程序类

<?php
class My_Core_SessionHandler_Database
{
    protected $dbh;
    protected $ipAddress = '';
    public function __construct() {   
        $this->dbh = My_Core_Config::get_dbinstance();
    }
    public function open($savePath, $sessionId) {
        return true;
    }
    public function close()  {
        return true;
    }
    public function read($sessionId) {                
        $query = "SELECT TOP 1 CAST(session as varchar(max)) as session
            FROM t_php_session
            WHERE php_session_id = '".$sessionId."'
                AND DATEADD(minute, ".My_Core_Config::get_value('session_timeout_period').", created) >= GETDATE()
                AND user_ip = '".$this->ipAddress."'";
        $stmt = $this->dbh->prepare($query);
        $stmt->execute();
        $result = $stmt->fetchColumn();       
        if ($result === false) {
            return '';
        }
        return $result;
    }
    public function write($sessionId, $sessionData) {
        $query = "
            SELECT id
            FROM t_php_session
            WHERE php_session_id = ?
        ";
        $stmt = $this->dbh->prepare($query);
        $stmt->execute(array($sessionId));
        $result = $stmt->fetchColumn();
        if (empty($result)) {            
            $query = "INSERT INTO t_php_session (php_session_id, session, user_ip, created) VALUES (?, CONVERT(VARBINARY(max), ?), ".$this->ipAddress.", GETDATE())";
            $stmt = $this->dbh->prepare($query);            
            $stmt->execute(array($sessionId, $sessionData));
        } else {
            $query = "
                UPDATE t_php_session
                SET session = CONVERT(VARBINARY(max), ?),
                    user_ip = ".$this->ipAddress.",
                    created = GETDATE()
                WHERE id = ?
            ";
            $stmt = $this->dbh->prepare($query);
            $stmt->execute(array($sessionData, $result));
        }
        return true;
    }
    public function destroy($sessionId) {
        $query = 'DELETE FROM t_php_session WHERE php_session_id = ?';
        $stmt = $this->dbh->prepare($query);
        $stmt->execute(array($sessionId));
        return true;
    }
    public function gc($maxlifetime) {
        $query = "
            DELETE FROM t_php_session
            WHERE DATEADD(minute, ".My_Core_Config::get_value('session_timeout_period').", created) < GETDATE()";
        $stmt = $this->dbh->prepare($query);
        $stmt->execute();
        return true;
    }
}

数据库表中会话字段的数据类型为varbinary（max）。我只是想这可能是问题所在，但不确定。

会话处理程序类的read方法的输出为：

My_Core_Session|a:1:{s:16:"My_Core_Session";a:4:{s:19:"previous_controller";N;s:15:"previous_action";N;s:18:"current_controller";s:16:"authentification";s:14:"current_action";s:5:"login";}}

Bootstrap.php中$_SESSION的输出为：

Array
(
    [My_Core_Session] => 
)

输出应该在哪里：

Array
(
    [My_Core_Session] => Array
        (
            [My_Core_Session] => Array
                (
                    [previous_controller] => 
                    [previous_action] => 
                    [current_controller] => authentification
                    [current_action] => login
                )
        )
)

该应用程序在Linux上运行良好，与相同的数据库一样，使用源代码，但环境不同，如Apache 2.2、FreeTDS、Dblib。我们刚刚将这个应用程序从Linux转移到Windows，并面临这个问题。