How to process a webhook request in php - json?

Question

PHP

I need to receive data from the service,
there the data is sent to the webhook in json format.
I do this, but nothing comes to me, the service says that everything works for them and my script gives a 500 error.
Although if you just open the script in the browser, everything is fine, it gives a 200 error and sends an empty letter to me.
$requestBody = file_get_contents('php://input');
mail($mail 'api', $requestBody);
where is the mistake?

Answer 1

Look at access log for a start. Then I'll try to just write their requests to the file. Most likely an error in sending the email.