Extract the TLD from a domain name, PHP tutorial code from http://www.tutdepot.com/parse-url-extract-domain-name/

extract-tld-from-domain.php

<?php
$url_parts = parse_url("http://mail.finalwebsites.co.uk");
$domain = $url_parts['host'];
$db = new mysqli(DB_SERVER, DB_USER, DB_PASSWORD, DB_NAME);
$res = $db->query("SELECT tld FROM domain_info ORDER BY LENGTH(tld) DESC");
// "ORDER BY LENGTH(tld)" will give first the co.uk and then the uk
while ($arr = $res->fetch_array(MYSQLI_ASSOC)) {
    $tmp_tld = substr($domain, -strlen(".".$arr['tld']));
    if ($tmp_tld == ".".$arr['tld']) { // You found the tld
        $tld = ltrim($arr['tld'], ".");
        $domainLeft = substr($domain, 0, -(strlen($tld) + 1)); // It will left the whatever, without the extension and the .
        if (strpos($domainLeft, ".") === false) { // It hasn't a subdomain
            $subDomain = "";
            $finalDomain = $domainLeft;
        } else {
            $domain_parts = explode(".", $domainLeft);
            $finalDomain = array_pop($domain_parts); // select the domain and remove it from the array
            $subDomain = implode(".", $domain_parts); // a subdomain can more then one parts seperated with dot's
        }
        echo "The tld is: ".$tld."<br>";
        echo "the domain name is :".$finalDomain."<br />";
        echo "the subdomain is: ";
        echo (!empty($subDomain)) ? $subDomain : "n/a";
        echo "<br>";
        break;
    }
}