Goo.gl URL Shortener Stopped Working (php/curl) - php

Question

For some reason my script stopped working today. When I look in the API control panel says I still have 100% left of usage. Any ideas? Did they change the auth way?
function url_small($url)
{
//This is the URL you want to shorten
$longUrl = $url;
$apiKey = '#####HIDDEN######';
//Get API key from : http://code.google.com/apis/console/
$postData = array('longUrl' => $longUrl, 'key' => $apiKey);
$jsonData = json_encode($postData);
$curlObj = curl_init();
curl_setopt($curlObj, CURLOPT_URL, 'https://www.googleapis.com/urlshortener/v1/url');
curl_setopt($curlObj, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curlObj, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curlObj, CURLOPT_HEADER, 0);
curl_setopt($curlObj, CURLOPT_HTTPHEADER, array('Content-type:application/json'));
curl_setopt($curlObj, CURLOPT_POST, 1);
curl_setopt($curlObj, CURLOPT_POSTFIELDS, $jsonData);
$response = curl_exec($curlObj);
//change the response json string to object
$json = json_decode($response);
curl_close($curlObj);
return $json->id;
}
Response
stdClass Object
(
[error] => stdClass Object
(
[errors] => Array
(
[0] => stdClass Object
(
[domain] => usageLimits
[reason] => dailyLimitExceededUnreg
[message] => Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.
[extendedHelp] => https://code.google.com/apis/console
)
)
[code] => 403
[message] => Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.
)
)

Answer 1

My below answer is no longer valid. Google now makes you use Firebase for URL Shortening. Easy to setup.
https://firebase.google.com/docs/dynamic-links/rest
So it turns out this old function that is displayed in multiple websites now needs the api key to be displayed in the URL section too for google to register the request to your account.
curl_setopt($curlObj, CURLOPT_URL, 'https://www.googleapis.com/urlshortener/v1/url');
switched to this
curl_setopt($curlObj, CURLOPT_URL, 'https://www.googleapis.com/urlshortener/v1/url?key='.$apiKey);