使用session_set_save_handler()函数，将Session的内容写入数据库

prepare($sql);
      $stmt->execute(array($PHPSESSID));
      if(!$result = $stmt->fetch(PDO::FETCH_ASSOC)){
        return '';
      }
      if(self::$ip == $result['client_ip']){
        self::destroy($PHPSESSID);
        return '';
      }
      if(($result['update_time']+self::$lifetime)prepare($sql);
      $stmt->execute(array($PHPSESSID));
      
      if($result=$stmt->fetch(PDO::FETCH_ASSOC)){        
        if($result['data'] != $data || self::$time > ($result['update_time']+30)){
          $sql = "update session set update_time=?,data=? where PHPSESSID = ?";
          $stmt = self::$handler->prepare($sql);
          $stmt->execute(array($self::$time,$data,$PHPSESSID));
        }
      }else{
        if(!empty($data)){
          try{
            $sql = "insert into session(PHPSESSID,update_time,client_ip,data) values(?,?,?,?)";
          }catch(PDOException $e){
            echo $e->getMessage();
          }
          $sth = self::$handler->prepare($sql);
          $sth->execute(array($PHPSESSID,self::$time,self::$ip,$data));
        }
      }
      return true;
    }
    
    public static function destroy($PHPSESSID){
      $sql = "delete from session where PHPSESSID = ?";
      $stmt = self::$handler->prepare($sql);
      $stmt->execute(array($PHPSESSID));
      return true;
    }
    public static function gc($lifetime){
      $sql = "delete from session where update_timeprepare($sql);
      $stmt->execute(array(self::$time-$lifetime));
      return true;
    }
  }
  //使用PDO连接数据库
  try{
    $pdo = new PDO("mysql:host=localhost;dbname=session","root","hwj193");
  }catch(PDOException $e){
    echo $e->getMessage();
  }
  //传递数据库资源
  Session::start($pdo);