How to get a url link for Bitly v4 on PHP?

Question

I tried following the replied guide on this post here How to shorten URL using PHP Bitly v4? but it doesn't really work.

this is my code so far with added variables to match what's on the bitly API documentaiton

$long_url = 'https://stackoverflow.com/questions/60732875/how-to-get-bitly-clicks-using-api-v4-with-php';
$group_guid = 'mygroupid';
$domain = 'bit.ly';
$apiv4 = 'https://api-ssl.bitly.com/v4/shorten';
$genericAccessToken = 'myaccesstoken';

$data = array(
    'long_url' => $long_url,
    'domain' => $domain,
    'group_guid' => $group_guid
);
$payload = json_encode($data);
echo $payload;

$header = array(
    "Authorization: Bearer ".$genericAccessToken,
    "Content-Type: application/json"
);

$ch = curl_init($apiv4);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
$result = curl_exec($ch);

print_r($result);

Echoed out the payload but no results being printed