How to check if a domain name is a CNAME in PHP

Question

How do I check if the URL accessing the page is the original URL or if it\'s a CNAME record.

For example, I have a site domain.com. Users can setup a CNAME

Answer 1

I think you have to query a DNS to know it, since this information does not usually come in request headers.

Take a look at the dns_get_record and checkdnsrr functions in PHP documentation.