problem with DQL and cache

<?php

// bootstrap

$cache = new \Doctrine\Common\Cache\ArrayCache();
$config = new Doctrine\ORM\Configuration();
$config->setQueryCacheImpl($cache);
$conn = array(
				'dbname' => $database_name,
				'user' => $cnx_user,
				'password' => $cnx_pass,
				'host' => $cnx_host,
				'driver' => $cnx_type,
				'charset' => 'utf8',
				'driverOptions' => array( 1002 => "SET NAMES 'utf8'" )
				);

			$em = Doctrine\ORM\EntityManager::create($conn, $config);

while(true){
   $dql = "SELECT s from Register s WHERE s.id = 1";
   $query = $em->createQuery($dql);
// the next line is optional, produces same result
   $query->useResultCache(false);
   $res = $query->getResult();
   $orm = reset($res);
   	
   echo " regiter id :".$orm->getId()."  field "$orm->getText()."\n";

}