I am not successful with PayPal-PHP-SKD code "payment->execute" - php

Question

I have successfully utilized PayPal-PHP-SKD to request a payment sending the user to the PayPal payment gateway sandbox with credentials and sandbox buyer account etc. Everything works and I get a request to the returnURL with $_GET variables success=true, paymentID, token and PayerID. My problem is in the next step which captures the paymentID and PayerID, creates objects for Payment PaymentExecution which seems to work OK but crashes when I execute the line "result = $payment->execute($exClaimPayment, $mPPcredentials);". If I comment out that line, the code works without error but when I include it the code crashes.
"result = $payment->execute($exClaimPayment, $mPPcredentials);"
if (isset($_GET['success'], $_GET['paymentId'], $_GET['PayerID'])) {
if ($_GET['success'] == 'true') {
$mSuccess = TRUE;
$mPaymentID = $_GET['paymentId'];
$mPayerID = $_GET['PayerID'];
$payment = Payment::get($mPaymentID, $mPPcredentials);
$exClaimPayment = New PaymentExecution();
$exClaimPayment->setPayerId($mPayerID);
$mProgress = 'in success after $exClaimPayment->setPayerId($mPayerID)';
try {
$mProgress = 'in try';
//result = $payment->execute($exClaimPayment, $mPPcredentials);
} catch(Exception $ex){
$errorMsg = json_decode($ex->getData());
}
}
} else {
$mSuccess = FALSE;
$mProgress = 'in NOT success';
}
In my envoronment, Win 10, Notepad++, FileZilla, Hostmonnster hosting and Chrome, I cannot see the error. It just crashes (with HTTP 500 ??)

Answer 1

I found my error! It was MY error.
The line:
result = $payment->execute($exClaimPayment, $mPPcredentials);
Should have been:
$result = $payment->execute($exClaimPayment, $mPPcredentials);
I have worked on this code for half a day and did not see my error until 5 minutes after I posted the question on StackOverflow.
My conspicuous errors in PHP often cost me a lot of time. I would benefit from an environment that would point out my syntax errors.
StackOverflow is a very good resource. Thanks!