In this call:
$Paypal = $API->selectOperation('GetExpressCheckoutDetails');
The response is supposed to provide more than what is returned. All I get back is:
[GetExpressCheckoutDetailsResponseDetails] => stdClass Object
[Token] => EC-4C4956437F975344J
[PayerInfo] => EC-4C4956437F975344J
There is no Payer, PayerID, PayerStatus, FirstName, LastName, Address, AddressStatus, or ContactPhone.
I am on Mac OS X 10.4.9, PHP 5.2.4.
Responding to my own post here. As I read over at PayPal Developer Community forums (where Israel has also commented), the bug was introduced with PHP 5.2.1 and above.
I can confirm that downgrading to 5.2.0 will allow this to work (obviously not ideal).