php - Class PDO not found in laravel 5.2 -

i have db helper , code in way:

<?php  namespace app\business;  use db;  class dbhelper{      private function dbconnectioninfo()       {      //$results = db::select('select username user_master');             //return "fetchuserlocation success". json_encode($results) ;         $pdo_db = db::connection()->getpdo() ;         $pdo_db->setattribute(pdo::attr_errmode, pdo::errmode_exception);         return $pdo_db;      }         function executeresultset($dbquery)     {         $pdo_object = dbhelper :: dbconnectioninfo();         $stmt = $pdo_object->prepare($dbquery);         $stmt->execute();         $results = $stmt->fetchall(pdo::fetch_assoc);         return $results;     }      function dbconnection()     {         return  dbhelper :: dbconnectioninfo();     } }  ?> 

when call return "fetchuserlocation success". json_encode($results) ; executed means db connection works when call function error : class 'app\business\pdo' not found how can use pdo in code. please suggest

write \pdo instead of pdo, because searching pdo inside namespace instead of searching 'pdo' in root namespace.