Why aren't cors headers being substituted?

Question

PHP

I send headers to the sides of the backend:

header("Access-Control-Allow-Origin: validate.ru");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400');

From the front I make an ajax request through jquery. And here's the question. Why, if I add such a line to the request parameters, then on the network tab, I will see that the server has inserted cors headers, and without this line, the cors headers are going somewhere. There is another clarification. The front is located on localhost. But the host configured. That is, requests go with the name origin=my_domain.ru
dataType: 'jsonp',

Answer 1

Quote from api.jquery.com/jquery.ajax
Those. when requesting dataType:'jsonp'CORS is not used. Hence the problem is not in jsonp, but in incorrect CORS setup. Unfortunately, the example that you gave does not give a complete picture of what is configured wrong.