How to solve problem with access to iframe?

Question

JavaScript

I need to get the content of an iframe from another domain.
In a php-file on another domain, I registered A, where the iframe is located in js, I registered An error appears in the browser:header('Access-Control-Allow-Origin: *');
document.domain = 'ds.wild.org.ru';

Uncaught SecurityError: Failed to set the 'domain' property on 'Document': 'ds.wild.org.ru' is not a suffix of 'wild.org.ru'.