I was reaching the youtube api quota limit while building my application so I added a developer key to the request and now I get a 403 error: Invalid Developer Key.
I've tried recreating my project and api key multiple times without any luck. I've tried adding the key to the URI as well as sending it in a header:
$c1 = curl_init($feedURL);
curl_setopt($c1, CURLOPT_HTTPHEADER, array(
'X-GData-Key: key=AIzaS...',
'GData-Version: 2'
));
My application is simple, all requested data is public, so I don't see a reason to use the Zend PHP Client.