从链接中提取域名

I'm looking for a bullet proof way to extract domain (with tld) from any given link - an eqivalent of dirname($path) let's call it domainname($link).

echo domainname("http://example.com/index.html?a=123%1231");

should print "example.com"

parse_url return value has a host key.

echo parse_url($url, PHP_URL_HOST);

More info: http://be.php.net/manual/en/function.parse-url.php