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Created April 11, 2013 20:27
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PHP code to get the domain name without subdomains (includes the tld, and the special types from IANA). Don't have support for unicode domain names.
* @param string $domain Pass $_SERVER['SERVER_NAME'] here
* @param bool $debug
* @debug bool $debug
* @return string
function get_domain($domain, $debug = false)
$original = $domain = strtolower($domain);
if (filter_var($domain, FILTER_VALIDATE_IP)) { return $domain; }
$debug ? print('<strong style="color:green">&raquo;</strong> Parsing: '.$original) : false;
$arr = array_slice(array_filter(explode('.', $domain, 4), function($value){
return $value !== 'www';
}), 0); //rebuild array indexes
if (count($arr) > 2)
$count = count($arr);
$_sub = explode('.', $count === 4 ? $arr[3] : $arr[2]);
$debug ? print(" (parts count: {$count})") : false;
if (count($_sub) === 2) // two level TLD
$removed = array_shift($arr);
if ($count === 4) // got a subdomain acting as a domain
$removed = array_shift($arr);
$debug ? print("<br>\n" . '[*] Two level TLD: <strong>' . join('.', $_sub) . '</strong> ') : false;
elseif (count($_sub) === 1) // one level TLD
$removed = array_shift($arr); //remove the subdomain
if (strlen($_sub[0]) === 2 && $count === 3) // TLD domain must be 2 letters
array_unshift($arr, $removed);
// non country TLD according to IANA
$tlds = array(
if (count($arr) > 2 && in_array($_sub[0], $tlds) !== false) //special TLD don't have a country
$debug ? print("<br>\n" .'[*] One level TLD: <strong>'.join('.', $_sub).'</strong> ') : false;
else // more than 3 levels, something is wrong
for ($i = count($_sub); $i > 1; $i--)
$removed = array_shift($arr);
$debug ? print("<br>\n" . '[*] Three level TLD: <strong>' . join('.', $_sub) . '</strong> ') : false;
elseif (count($arr) === 2)
$arr0 = array_shift($arr);
if (strpos(join('.', $arr), '.') === false
&& in_array($arr[0], array('localhost','test','invalid')) === false) // not a reserved domain
$debug ? print("<br>\n" .'Seems invalid domain: <strong>'.join('.', $arr).'</strong> re-adding: <strong>'.$arr0.'</strong> ') : false;
// seems invalid domain, restore it
array_unshift($arr, $arr0);
$debug ? print("<br>\n".'<strong style="color:gray">&laquo;</strong> Done parsing: <span style="color:red">' . $original . '</span> as <span style="color:blue">'. join('.', $arr) ."</span><br>\n") : false;
return join('.', $arr);
$urls = array(
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'localhost' => 'localhost',
'www.localhost' => 'localhost',
'subdomain.localhost' => 'localhost',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'test' => 'test',
'www.test' => 'test',
'subdomain.test' => 'test',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'' => '',
'::1' => '::1',
$failed = 0;
$total = count($urls);
foreach ($urls as $from => $expected)
$from = get_domain($from, true);
if ($from !== $expected)
print("<div style='color:fuchsia;'>expected {$from} to be {$expected}</div>");
if ($failed)
print("{$failed} tests failed out of {$total}");
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neo22s commented Feb 18, 2015

Doesn't work for domains with TLD of len = 2:

'' => '',
'' => '',


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Nice job. Thanks a lot man! :)

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NabiKAZ commented Jun 2, 2016

does not work for and return

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pocesar commented Aug 8, 2016

the best thing is to create a lookup array with all available TLDs from IANA, a lot have been added since 2013 including having support for punycode a bit of manual setup at first, but performance, and strictly compliant to the list

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very cool! Saves some custom code writting! Thanks!

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Well written code for finding main domain, thanks...

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If you want all TLD list, you can find it updated in
But if you want the list for PHP language you can copy here:

$tlds = array(
    # Version 2022060900, Last Updated Thu Jun  9 07:07:02 2022 UTC

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