class DbHelpClass    {        private $conn;        private $qxId;        private $ret;                function __construct()        {            $path="../../App_Data/sd#f#45G_!.mdb";            $constr="DRIVER={Microsoft Access Driver (*.mdb)}; DBQ=".realpath($path);             $this->conn= new PDO("odbc:$constr") or die ("PDO Connection faild.");        }                /*读取*/        function Read($sql,$params=array())        {            $bind=$this->conn->prepare($sql);            $arrKeys=array_keys($params);            foreach($arrKeys as $row)            {                $bind->bindValue(":".$row,$params[$row]);            }            $bind->execute() or die('sql error:'.$sql);            $result=$bind->fetchAll();                        return $result;        }                /*添加,修改需调用此方法*/        function Edit($sql,$params=array())        {            $bind=$this->conn->prepare($sql);            $arrKeys=array_keys($params);            foreach($arrKeys as $row)            {                $bind->bindValue(":".$row,$params[$row]);                            }                        $a=$bind->execute() or die('sql error');            return $a;        }    }    $dbh =new DbHelpClass();