public function BillUser($billUserReq, $apiCredential = null)
{
$apiContext = new PPApiContext($this->config);
$handlers = array(new PPMerchantServiceHandler($apiCredential, self::$SDK_NAME, self::$SDK_VERSION));
$this->setStandardParams($billUserReq->BillUserRequest);
$ret = new BillUserResponseType();
$resp = $this->call('PayPalAPI', 'BillUser', $billUserReq, $apiContext, $handlers);
$ret->init(PPUtils::xmlToArray($resp));
return $ret;
}