PHP Getting Domain Name From Subdomain

I need to write a function to parse variables which contain domain names. It’s best I explain this with an example, the variable could contain any of these things:

here.example.com
example.com
example.org
here.example.org

But when passed through my function all of these must return either example.com or example.co.uk, the root domain name basically. I’m sure I’ve done this before but I’ve been searching Google for about 20 minutes and can’t find anything. Any help would be appreciated.

EDIT: Ignore the .co.uk, presume that all domains going through this function have a 3 letter TLD.

Answer

Stackoverflow Question Archive:

• How to get domain name from url?
• Check if domain equals value?
• How do I get the base url?

---

print get_domain("http://somedomain.co.uk"); // outputs 'somedomain.co.uk'

function get_domain($url)
{
  $pieces = parse_url($url);
  $domain = isset($pieces['host']) ? $pieces['host'] : '';
  if (preg_match('/(?P<domain>[a-z0-9][a-z0-9-]{1,63}.[a-z.]{2,6})$/i', $domain, $regs)) {
    return $regs['domain'];
  }
  return false;
}