How to solve the problem of passing headers?

Question

MODX

Hello. Such a mistake.
XMLHttpRequest cannot load http://site.newserver.ru/ajax.json(this is a copy of the main domain) Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin ' xn----7sbbag3bufvkjkjkl.xn--p1ai ' is therefore not allowed access.
Esteemed, it is written add header header
<?php header("Access-Control-Allow-Origin: *");?>
Added to the beginning of the file
Didn't work. Maybe it's in Cyrillic?
Maybe someone did? Faced? Thank you!