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();