session入mysql

<?phpini_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'];