Cannot Verify Shopify Webhook - php

Question

I have setup a webhook in shopify via settings > notifications > webhooks and entered a heroku app URL. My heroku app is in php and I run the verification function found here: https://shopify.dev/tutorials/manage-webhooks and when I open my app I get a blank response. I am not sure if this is something I am doing wrong on my heroku app, or if I am missing something. The goal here is to grab the json data after the event I have selected is ran, then to send that data to via third party api. But to start I just want to be able to verify that my heroku app is receiving the payload. Is there more I need to add to my php file in order to verify? (php noob here). Below is the code I am running in my php file, and yes I am using my shared secret found in the webhooks section.
<?php
define('SHOPIFY_APP_SECRET', 'my_shared_secret');
function verify_webhook($data, $hmac_header)
{
$calculated_hmac = base64_encode(hash_hmac('sha256', $data, SHOPIFY_APP_SECRET, true));
return hash_equals($hmac_header, $calculated_hmac);
}
$hmac_header = $_SERVER['HTTP_X_SHOPIFY_HMAC_SHA256'];
$data = file_get_contents('php://input');
$verified = verify_webhook($data, $hmac_header);
error_log('Webhook verified: '.var_export($verified, true)); //check error.log to see the result
?>

Answer 1

If I am not mistaken you cannot test webhooks that way as the admin does not use your API key as it has no idea who you are when in the admin. So if you have a heroku App and it has an API key, use that API key to first off establish the webhook, verify you created it with the API, and then sit around and test your actual endpoint with Shopify Admin itself. That is how it works AFAIK.
The other verification in the admin is mickey mouse and meant to just throw data at any old endpoint with no validation.