Free Domain name registrar finder script

This little tool will allow you to find the registrar of any domain by checking it’s WHOIS information.
Just enter any domain name and it will show you the registrar's name..

Source:
http://www.bhawanigarg.com/how-to-find-the-registrar-of-a-domain-via-php/

Demo:
http://www.bhawanigarg.com/domain/