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

Question

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 use parse_url() to do this:

$url = 'http://www.example.com';
$domain = parse_url($url, PHP_URL_HOST);
$domain = str_replace('www.','',$domain);

In this example, $domain should contain example.com, irrespective of it having www or not. It also works for a domain such as .co.uk

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.

Here are a couple simple functions to get the root domain (example.com) from a normal or long domain (test.sub.domain.com) or url (http://www.example.com).

/**
 * Get root domain from full domain
 * @param string $domain
 */
public function getRootDomain($domain)
{
    $domain = explode('.', $domain);

    $tld = array_pop($domain);
    $name = array_pop($domain);

    $domain = "$name.$tld";

    return $domain;
}

/**
 * Get domain name from url
 * @param string $url
 */
public function getDomainFromUrl($url)
{
    $domain = parse_url($url, PHP_URL_HOST);
    $domain = $this->getRootDomain($domain);

    return $domain;
}

Following code will trim protocol, domain and port from absolute URL:

$urlWithoutDomain = preg_replace('#^.+://[^/]+#', '', $url);