How do you strip out the domain name from a URL in php?

Im looking for a method (or function) to strip out the domain.ext part of any URL thats fed into the function. The domain extension can be anything (.com, .co.uk, .nl, .whatever), and the URL thats fed into it can be anything from http://www.domain.com to www.domain.com/path/script.php?=whatever

Whats the best way to go about doing this?

parse_url turns a URL into an associative array:

php > $foo = "http://www.example.com/foo/bar?hat=bowler&accessory=cane";
php > $blah = parse_url($foo);
php > print_r($blah);
Array
(
    [scheme] => http
    [host] => www.example.com
    [path] => /foo/bar
    [query] => hat=bowler&accessory=cane
)

You can also write a regular expression to get exactly what you want.

Here is my attempt at it:

$pattern = '/\w+\..{2,3}(?:\..{2,3})?(?:$|(?=\/))/i';
$url = 'http://www.example.com/foo/bar?hat=bowler&accessory=cane';
if (preg_match($pattern, $url, $matches) === 1) {
    echo $matches[0];
}

The output is:

example.com

This pattern also takes into consideration domains such as 'example.com.au'.

Note: I have not consulted the relevant RFC.