How to check a domain age using php

Hello I was wondering if there is a nice way to find out what is the age of a specific domain.

But I want to find out a way to do this programmatically asking the DNS to check a domain age using php and not from an online tool.

I am searching on the internet to find out how google is checking my domain age and other SEO tools.

Is this information private for a domain where you must have special permissions to ask what a domains age is? And if yes? How come google knows my domain age? noone asked my domains age.. how come they know it?

Solution

You want WHOIS, most recently defined in RFC3912:

$ whois stackoverflow.com

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

   Domain Name: STACKOVERFLOW.COM
   Registrar: GODADDY.COM, INC.
   Whois Server: whois.godaddy.com
   Referral URL: http://registrar.godaddy.com
   Name Server: NS1.SERVERFAULT.COM
   Name Server: NS2.SERVERFAULT.COM
   Name Server: NS3.SERVERFAULT.COM
   Status: clientDeleteProhibited
   Status: clientRenewProhibited
   Status: clientTransferProhibited
   Status: clientUpdateProhibited
   Updated Date: 30-nov-2010
   Creation Date: 26-dec-2003
   Expiration Date: 26-dec-2014
   
   [...]