session入mysql

<?php  ini_set("session.save_handler","user");    //session.gc_probability = 1 分子    ini_set("session.gc_probability",1);    //session.gc_divisor = 1000 分母    ini_set("session.gc_divisor",2);    //session.gc_maxlifetime = 1440 垃圾回收时间，session有效期    session_set_save_handler( "open","close","read","write","destroy","gc" );  //连接数据库    function open(){        @$link = mysql_connect('127.0.0.1', 'root', 'root');        mysql_query('set names utf8');        mysql_query('use wangbin');    }    function close(){        mysql_close();    }    function read($sess_id){        $sql = "select session_data from `session` where session_id = '$sess_id'";        $result = mysql_query($sql);        if($rows = mysql_fetch_assoc($result)){          return $rows['session_data']; }      else{          return '';      }    }    function write($sess_id,$sess_data){        $sql = "insert into `session` (session_id,session_data,session_time) values('$sess_id','$sess_data', now()) on duplicate key update session_data = '$sess_data' , session_time = now()";  //这是为了gc()        return mysql_query($sql);        }    function destroy($sess_id){        echo __FUNCTION__;        $sql = "delete from `session` where session_id = '$sess_id'";        return mysql_query($sql);        }    function gc($sess_id){        $maxlifetime = ini_set("session.gc_maxlifetime");        echo __FUNCTION__;        $sql = "delete from `session` where now()-session_time > '$maxlifetime' ";        return mysql_query($sql);    }    header("content-type:text/html;charset=utf8");    session_start();    $_SESSION['name']='aa';    //echo session_id();    echo $_SESSION['name'];