PayPal\Service\PayPalAPIInterfaceServiceService::DoReferenceTransaction PHP Method

    public function DoReferenceTransaction($doReferenceTransactionReq, $apiCredential = null)
    {
        $apiContext = new PPApiContext($this->config);
        $handlers = array(new PPMerchantServiceHandler($apiCredential, self::$SDK_NAME, self::$SDK_VERSION));
        $this->setStandardParams($doReferenceTransactionReq->DoReferenceTransactionRequest);
        $ret = new DoReferenceTransactionResponseType();
        $resp = $this->call('PayPalAPIAA', 'DoReferenceTransaction', $doReferenceTransactionReq, $apiContext, $handlers);
        $ret->init(PPUtils::xmlToArray($resp));
        return $ret;
    }

}
$RTRequestDetails->PaymentDetails = $paymentDetails;
$RTRequestDetails->ReferenceID = $_REQUEST['referenceID'];
$RTRequestDetails->PaymentAction = $_REQUEST['paymentAction'];
$RTRequestDetails->PaymentType = $_REQUEST['paymentType'];
$RTRequest = new DoReferenceTransactionRequestType();
$RTRequest->DoReferenceTransactionRequestDetails = $RTRequestDetails;
$RTReq = new DoReferenceTransactionReq();
$RTReq->DoReferenceTransactionRequest = $RTRequest;
/*
## Creating service wrapper object
Creating service wrapper object to make API call and loading
Configuration::getAcctAndConfig() returns array that contains credential and config parameters
*/
$paypalService = new PayPalAPIInterfaceServiceService(Configuration::getAcctAndConfig());
try {
    /* wrap API method calls on the service object with a try catch */
    $RTResponse = $paypalService->DoReferenceTransaction($RTReq);
} catch (Exception $ex) {
    include_once "../Error.php";
    exit;
}
if (isset($RTResponse)) {
    echo "<table>";
    echo "<tr><td>Ack :</td><td><div id='Ack'>{$RTResponse->Ack}</div> </td></tr>";
    echo "</table>";
    echo "<pre>";
    print_r($RTResponse);
    echo "</pre>";
}
require_once '../Response.php';