I don’t know how to phrase this better, mainly because I dont really know how DNS fully works.
Given a URL and an IP, is it possible to tell PHP to make all requests to that IP AS the given URL instead of the real DNS (Just as if you edited your hosts file locally)?
The only solution I see is to run your own bind server, and tell your clients to use your bind server. You then have full control how a name is routed to a IP.