PayPalAPIInterfaceServiceService::SetExpressCheckout() returns null response object - paypal

Question

I'm using Yii to build an application that requires payments through PayPal. After a lot of digging, I found that ExpressCheckout is the method to use. The code below worked fine some time ago (some (?) weeks ago, I suppose before PayPal rolling out their new developer platform), using version 1.2.95 of the PHP SDK. Now, using the latest version v.2.2.98, the code fails.
require_once(Yii::getPathOfAlias('application.libraries.paypal') . '/PPBootStrap.php');
$logger = new PPLoggingManager('SetExpressCheckout');
$PaymentDetails = new PaymentDetailsType();
$PaymentDetails->OrderTotal = $PaymentDetails->ItemTotal =
new BasicAmountType('USD', $subscription->price);
$PaymentDetails->PaymentAction = "Sale";
$PaymentDetails->OrderDescription = $subscription->description;
$setECReqDetails = new SetExpressCheckoutRequestDetailsType();
$setECReqDetails->PaymentDetails[0] = $PaymentDetails;
$setECReqDetails->CancelURL = 'someCancelUrl';
$setECReqDetails->ReturnURL = 'someReturnUrl';
$setECReqType = new SetExpressCheckoutRequestType();
$setECReqType->SetExpressCheckoutRequestDetails = $setECReqDetails;
$setECReq = new SetExpressCheckoutReq();
$setECReq->SetExpressCheckoutRequest = $setECReqType;
$paypalService = new PayPalAPIInterfaceServiceService();
$ok = TRUE;
try {
$setECResponse = $paypalService->SetExpressCheckout($setECReq);
if($setECResponse && strtoupper($setECResponse->Ack) =='SUCCESS') {
$token = $setECResponse->Token;
// Redirect to paypal.com here
$this->redirect(
'https://www.sandbox.paypal.com/webscr?cmd=_express-checkout&token=' . $token);
}
}
catch (Exception $ex) {
Yii::trace(__METHOD__ . ': Exception while interacting with PayPal API, error: '
. $ex->getMessage());
$ok = FALSE;
}
The offending line is:
$setECResponse = $paypalService->SetExpressCheckout($setECReq);
In PayPalAPIInterfaceServiceService::SetExpressCheckout(), these two lines:
$resp = $this->call('PayPalAPIAA', 'SetExpressCheckout', $setExpressCheckoutReq, $apiCredential);
$ret->init(PPUtils::xmlToArray($resp));
are the issue. $resp is null, so the next line fails at the PPUtils::xmlToArray($resp) method call.
Obviously, either I'm missing something here, or PayPal does something wrong.
Any help?

Answer 1

After a lot of debugging, the cause of the issue was that the service.EndPoint.PayPalAPI parameter was not defined in sdk_config.ini. For some reason that I don't recall, this parameter was deleted from the working config file from the previous version.
Now, the express checkout method works fine, even with the latest 2.3.100 version of the API.