How to run the iDEAL API?

Question

PHP

Good evening.
Maybe someone knows how to turn on the API https://developer.paycheckout.com
I made a pay.php page and put this code there:
But an empty page comes out, nothing more.
Support from this cantor does not want to help, says read the API, but I don’t see a single example of how to integrate it into my site.

<?php
require_once('PayCheckout/src/PayCheckout/autoloader.php');
// Prepare the Generic payment 
$apiMessage = PayCheckout\Api\Payment\Generic::create(PayCheckout\PaymentMethod::IDEAL,'30','1-maand - CV-DataBank ',35695,PayCheckout\Currency::C_EUR,'10.129.89.178',null,null,null);
// Set return url override 
$apiMessage->payment_overrideConfiguredReturnUrls('a.php?page=66','a.php?page=67','a.php?page=68');
// Create an executor instance 
$apiExecutor = new PayCheckout\ApiExecutor(xxxxx,'xxxxxxx',true);
// Execute the call and receive result 
$response = $apiExecutor->execute($apiMessage);
// Analyze result
 if ($response->getApiResult() != PayCheckout\ApiResult::FAILED) { 
// Success or Success with warning, test if we should redirect etc..
} else { 
// Analyze why it failed
}
?>

There should be a button - Buy
by clicking to open this IDEAL for payment and that's it
But I can't run anything.