关于Session入库的有关问题

<?php<br />class SessionDBTool {<br />    //MySQLDB类的对象<br />    private $db;<br /><br />	public function __construct(){<br />		//设置处理器方法<br />		ini_set('session.save_handler', 'user');<br />		session_set_save_handler(<br />			array($this,'sess_open'),<br />			array($this,'sess_close'),<br />			array($this,'sess_read'),<br />			array($this,'sess_write'),<br />			array($this,'sess_destroy'),<br />			array($this,'sess_gc')<br />			);<br />		//开启session<br />		session_start();<br />	}<br /><br />	public function sess_open(){<br />        $this->db = MySQLDB::getInstance($GLOBALS['config']['database']);<br />	}<br /><br />	public function sess_close(){<br />        return true;<br />	}<br /><br />	public function sess_read($sess_id){<br />        $sql = "select sess_data from it_session where sess_id = '$sess_id'";<br />        return (string)$this->db->fetchColumn($sql);<br />    }<br /><br />	public function sess_write($sess_id,$sess_data){<br />        $expire = time();<br />        $sql = "insert into it_session values('$sess_id','$sess_data',$expire) on duplicate key update sess_data = '$sess_data',expire = $expire";<br />        return $this->db->query($sql);<br />	}<br /><br />	public function sess_destroy($sess_id){<br />        $sql = "delete from it_session where sess_id = '$sess_id'";<br />        return $this->db->query($sql);<br />	}<br /><br />	public function sess_gc($ttl){<br />        $last_time = time() - $ttl;<br />        $sql = "delete from it_session where expire < $last_time";<br />        return $this->db->query($sql);<br />	}<br />}<br /><br />?>

<?php<br />/**<br /> * Created by PhpStorm.<br /> * User: DoubleJack<br /> * Date: 2015/5/13<br /> * Time: 23:18<br /> */<br />    class BackPlatformController extends Controller {<br />        /**<br />         * 构造函数，使其自动checklogin()<br />         */<br />        public function __construct(){<br />            //开启session<br />            $this->initSession();<br />            //验证是否登陆<br />            $this->checkLogin();<br /><br />        }<br />        /**<br />         * 初始化session入库<br />         */<br />        protected function initSession(){<br />           new SessionDBTool;<br />        }<br /><br />        /**<br />         * 验证当前用户是否登陆<br />         */<br />        protected function checkLogin(){<br />            //判断是否登录<br />            if(CONTROLLER=="admin" && (ACTION=="login" || ACTION=="signin")) {<br />                //不需要<br />            }else{<br />                //需要<br />                    if(isset($_SESSION['is_login']) && $_SESSION['is_login'] == 'YES'){<br />                        //载入后台的模板<br />                        require CURR_VIEW_DIR . 'index.html';<br />                 //继续执行<br />                }else{<br /><br />                    $this->jump('index.php?p=back&c=Admin&a=login','请先登录',2);<br />                }<br />            }<br />        }<br /><br /><br /><br />    }