Parse URL and extract the domain name

<?php
$url_parts = parse_url("http://mail.xxxxxxx.net");
$domain = $url_parts['host'];
$res = mysql_query("SELECT tld FROM domain_info ORDER BY LENGTH(tld) DESC");
// "ORDER BY LENGTH(tld)" will give first the co.uk and then the uk
while ($arr = mysql_fetch_assoc($res)) {
    $tmp_tld = substr($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;
    }
}
?>

DATABASE

CREATE TABLE `domain_info` (
  `tld` varchar(20) collate latin1_general_ci NOT NULL default '',
  `whois_server` varchar(100) collate latin1_general_ci NOT NULL default '',
  `is_free` varchar(100) collate latin1_general_ci NOT NULL default '',
  UNIQUE KEY `tld` (`tld`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;

--
-- Dumping data for table `domain_info`
--

INSERT INTO `domain_info` (`tld`, `whois_server`, `is_free`) VALUES
('ac', 'whois.nic.ac', 'No match'),
('ac.cn', 'whois.cnnic.net.cn', 'no matching record'),
('ac.jp', 'whois.nic.ad.jp', 'No match'),
('ac.uk', 'whois.ja.net', 'No such domain'),
('ad.jp', 'whois.nic.ad.jp', 'No match'),
('adm.br', 'whois.nic.br', 'No match'),
('adv.br', 'whois.nic.br', 'No match'),
('aero', 'whois.information.aero', 'is available'),
('ag', 'whois.nic.ag', 'Not found'),
('agr.br', 'whois.nic.br', 'No match'),
('ah.cn', 'whois.cnnic.net.cn', 'No entries found'),
('al', 'whois.ripe.net', 'No entries found'),
('am', 'whois.amnic.net', 'No match'),
('am.br', 'whois.nic.br', 'No match'),
('arq.br', 'whois.nic.br', 'No match'),
('art.br', 'whois.nic.br', 'No match'),
('as', 'whois.nic.as', 'Domain Not Found'),
('asn.au', 'whois.aunic.net', 'No Data Found'),
('at', 'whois.nic.at', 'nothing found'),
('ato.br', 'whois.nic.br', 'No match'),
('au', 'whois.aunic.net', 'No Data Found'),
('av.tr', 'whois.nic.tr', 'Not found in database'),
('az', 'whois.ripe.net', 'no entries found'),
('ba', 'whois.ripe.net', 'No match for'),
('be', 'whois.geektools.com', 'No such domain'),
('bel.tr', 'whois.nic.tr', 'Not found in database'),
('bg', 'whois.digsys.bg', 'does not exist'),
('bio.br', 'whois.nic.br', 'No match'),
('biz', 'whois.biz', 'Not found'),
('biz.tr', 'whois.nic.tr', 'Not found in database'),
('bj.cn', 'whois.cnnic.net.cn', 'No entries found'),
('bmd.br', 'whois.nic.br', 'No match'),
('br', 'whois.registro.br', 'No match'),
('by', 'whois.ripe.net', 'no entries found'),
('ca', 'whois.cira.ca', 'Status: AVAIL'),
('cc', 'whois.nic.cc', 'No match'),
('cd', 'whois.cd', 'No match'),
('ch', 'whois.nic.ch', 'We do not have an entry'),
('cim.br', 'whois.nic.br', 'No match'),
('ck', 'whois.ck-nic.org.ck', 'No entries found'),
('cl', 'whois.nic.cl', 'no existe'),
('cn', 'whois.cnnic.net.cn', 'No entries found'),
('cng.br', 'whois.nic.br', 'No match'),
('cnt.br', 'whois.nic.br', 'No match'),
('co.at', 'whois.nic.at', 'nothing found'),
('co.jp', 'whois.nic.ad.jp', 'No match'),
('co.uk', 'whois.nic.uk', 'No match for'),
('com', 'whois.crsnic.net', 'No match'),
('com.au', 'whois.aunic.net', 'No Data Found'),
('com.br', 'whois.nic.br', 'No match'),
('com.cn', 'whois.cnnic.net.cn', 'No entries found'),
('com.eg', 'whois.ripe.net', 'No entries found'),
('com.hk', 'whois.hknic.net.hk', 'No Match for'),
('com.mx', 'whois.nic.mx', 'Nombre del Dominio'),
('com.ru', 'whois.ripn.ru', 'No entries found'),
('com.tr', 'whois.nic.tr', 'Not found in database'),
('com.tw', 'whois.twnic.net', 'NO MATCH TIP'),
('conf.au', 'whois.aunic.net', 'No entries found'),
('cq.cn', 'whois.cnnic.net.cn', 'No entries found'),
('csiro.au', 'whois.aunic.net', 'No Data Found'),
('cx', 'whois.nic.cx', 'No match'),
('cy', 'whois.ripe.net', 'no entries found'),
('cz', 'whois.nic.cz', 'No data found'),
('de', 'whois.denic.de', 'not found'),
('dk', 'whois.dk-hostmaster.dk', 'No entries found'),
('dr.tr', 'whois.nic.tr', 'Not found in database'),
('dz', 'whois.ripe.net', 'no entries found'),
('ecn.br', 'whois.nic.br', 'No match'),
('edu', 'whois.crsnic.net', 'No match'),
('edu.au', 'whois.aunic.net', 'No Data Found'),
('edu.br', 'whois.nic.br', 'No match'),
('edu.tr', 'whois.nic.tr', 'Not found in database'),
('ee', 'whois.eenet.ee', 'NOT FOUND'),
('eg', 'whois.ripe.net', 'No entries found'),
('emu.id.au', 'whois.aunic.net', 'No Data Found'),
('eng.br', 'whois.nic.br', 'No match'),
('es', 'whois.ripe.net', 'No entries found'),
('esp.br', 'whois.nic.br', 'No match'),
('etc.br', 'whois.nic.br', 'No match'),
('eti.br', 'whois.nic.br', 'No match'),
('eu', 'whois.eu', 'Status:      FREE'),
('eun.eg', 'whois.ripe.net', 'No entries found'),
('far.br', 'whois.nic.br', 'No match'),
('fi', 'whois.ripe.net', 'No entries found'),
('fj', 'whois.usp.ac.fj', ''),
('fj.cn', 'whois.cnnic.net.cn', 'No entries found'),
('fm.br', 'whois.nic.br', 'No match'),
('fnd.br', 'whois.nic.br', 'No match'),
('fo', 'whois.ripe.net', 'no entries found'),
('fot.br', 'whois.nic.br', 'No match'),
('fr', 'whois.nic.fr', 'No entries found'),
('fst.br', 'whois.nic.br', 'No match'),
('g12.br', 'whois.nic.br', 'No match'),
('gb', 'whois.ripe.net', 'No match for'),
('gb.com', 'whois.nomination.net', 'No match for'),
('gb.net', 'whois.nomination.net', 'No match for'),
('gd.cn', 'whois.cnnic.net.cn', 'No entries found'),
('ge', 'whois.ripe.net', 'no entries found'),
('gen.tr', 'whois.nic.tr', 'Not found in database'),
('ggf.br', 'whois.nic.br', 'No match'),
('gl', 'whois.ripe.net', 'no entries found'),
('gob.mx', 'whois.nic.mx', 'Nombre del Dominio'),
('gov.au', 'whois.aunic.net', 'No Data Found'),
('gov.br', 'whois.nic.br', 'No match'),
('gov.cn', 'whois.cnnic.net.cn', 'No entries found'),
('gov.hk', 'whois.hknic.net.hk', 'No Match for'),
('gov.tr', 'whois.nic.tr', 'Not found in database'),
('gr', 'whois.ripe.net', 'no entries found'),
('gr.jp', 'whois.nic.ad.jp', 'No match'),
('gs', 'whois.adamsnames.tc', 'is not registered'),
('gs.cn', 'whois.cnnic.net.cn', 'No entries found'),
('gx.cn', 'whois.cnnic.net.cn', 'No entries found'),
('gz.cn', 'whois.cnnic.net.cn', 'No entries found'),
('ha.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hb.cn', 'whois.cnnic.net.cn', 'No entries found'),
('he.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hi.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hk', 'whois.hknic.net.hk', 'No Match for'),
('hk.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hl.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hm', 'whois.registry.hm', '(null)'),
('hn.cn', 'whois.cnnic.net.cn', 'No entries found'),
('hu', 'whois.ripe.net', 'MAXCHARS:500'),
('id.au', 'whois.aunic.net', 'No Data Found'),
('idv.tw', 'whois.twnic.net', 'NO MATCH TIP'),
('ie', 'whois.domainregistry.ie', 'no match'),
('il', 'whois.isoc.org.il', 'No data was found'),
('imb.br', 'whois.nic.br', 'No match'),
('ind.br', 'whois.nic.br', 'No match'),
('inf.br', 'whois.nic.br', 'No match'),
('info', 'whois.afilias.info', 'Not found'),
('info.au', 'whois.aunic.net', 'No Data Found'),
('info.tr', 'whois.nic.tr', 'Not found in database'),
('int', 'whois.iana.org', 'not found'),
('is', 'whois.isnic.is', 'No entries found'),
('it', 'whois.nic.it', 'No entries found'),
('jl.cn', 'whois.cnnic.net.cn', 'No entries found'),
('jor.br', 'whois.nic.br', 'No match'),
('jp', 'whois.nic.ad.jp', 'No match'),
('js.cn', 'whois.cnnic.net.cn', 'No entries found'),
('jx.cn', 'whois.cnnic.net.cn', 'No entries found'),
('k12.tr', 'whois.nic.tr', 'Not found in database'),
('ke', 'whois.rg.net', 'No match for'),
('kr', 'whois.krnic.net', 'is not registered'),
('la', 'whois.nic.la', 'NO MATCH'),
('lel.br', 'whois.nic.br', 'No match'),
('li', 'whois.nic.ch', 'We do not have an entry'),
('lk', 'whois.nic.lk', 'No domain registered'),
('ln.cn', 'whois.cnnic.net.cn', 'No entries found'),
('lt', 'ns.litnet.lt', 'No matches found'),
('ltd.uk', 'whois.nic.uk', 'No match for'),
('lu', 'whois.dns.lu', 'No entries found'),
('lv', 'whois.ripe.net', 'no entries found'),
('ma', 'whois.ripe.net', 'No entries found'),
('mat.br', 'whois.nic.br', 'No match'),
('mc', 'whois.ripe.net', 'No entries found'),
('md', 'whois.ripe.net', 'No match for'),
('me.uk', 'whois.nic.uk', 'No match for'),
('med.br', 'whois.nic.br', 'No match'),
('mil', 'whois.nic.mil', 'No match'),
('mil.br', 'whois.nic.br', 'No match'),
('mil.tr', 'whois.nic.tr', 'Not found in database'),
('mk', 'whois.ripe.net', 'No match for'),
('mn', 'whois.nic.mn', 'Domain not found'),
('mo.cn', 'whois.cnnic.net.cn', 'No entries found'),
('ms', 'whois.adamsnames.tc', 'is not registered'),
('mt', 'whois.ripe.net', 'No Entries found'),
('mus.br', 'whois.nic.br', 'No match'),
('mx', 'whois.nic.mx', 'Nombre del Dominio'),
('name', 'whois.nic.name', 'No match'),
('name.tr', 'whois.nic.tr', 'Not found in database'),
('ne.jp', 'whois.nic.ad.jp', 'No match'),
('net', 'whois.crsnic.net', 'No match'),
('net.au', 'whois.aunic.net', 'No Data Found'),
('net.br', 'whois.nic.br', 'No match'),
('net.cn', 'whois.cnnic.net.cn', 'No entries found'),
('net.eg', 'whois.ripe.net', 'No entries found'),
('net.hk', 'whois.hknic.net.hk', 'No Match for'),
('net.lu', 'whois.dns.lu', 'No entries found'),
('net.mx', 'whois.nic.mx', 'Nombre del Dominio'),
('net.ru', 'whois.ripn.ru', 'No entries found'),
('net.tr', 'whois.nic.tr', 'Not found in database'),
('net.tw', 'whois.twnic.net', 'NO MATCH TIP'),
('net.uk', 'whois.nic.uk', 'No match for'),
('nl', 'whois.domain-registry.nl', 'is not a registered domain'),
('nm.cn', 'whois.cnnic.net.cn', 'No entries found'),
('no', 'whois.norid.no', 'no matches'),
('no.com', 'whois.nomination.net', 'No match for'),
('nom.br', 'whois.nic.br', 'No match'),
('not.br', 'whois.nic.br', 'No match'),
('ntr.br', 'whois.nic.br', 'No match'),
('nu', 'whois.nic.nu', 'NO MATCH for'),
('nx.cn', 'whois.cnnic.net.cn', 'No entries found'),
('nz', 'whois.domainz.net.nz', 'Not Listed'),
('odo.br', 'whois.nic.br', 'No match'),
('oop.br', 'whois.nic.br', 'No match'),
('or.at', 'whois.nic.at', 'nothing found'),
('or.jp', 'whois.nic.ad.jp', 'No match'),
('org', 'whois.pir.org', 'NOT FOUND'),
('org.au', 'whois.aunic.net', 'No Data Found'),
('org.br', 'whois.nic.br', 'No match'),
('org.cn', 'whois.cnnic.net.cn', 'No entries found'),
('org.hk', 'whois.hknic.net.hk', 'No Match for'),
('org.lu', 'whois.dns.lu', 'No entries found'),
('org.ru', 'whois.ripn.ru', 'No entries found'),
('org.tr', 'whois.nic.tr', 'Not found in database'),
('org.tw', 'whois.twnic.net', 'NO MATCH TIP'),
('org.uk', 'whois.nic.uk', 'No match for'),
('pk', 'whois.pknic.net', 'is not registered'),
('pl', 'whois.ripe.net', 'No information about'),
('plc.uk', 'whois.nic.uk', 'No match for'),
('pol.tr', 'whois.nic.tr', 'Not found in database'),
('pp.ru', 'whois.ripn.ru', 'No entries found'),
('ppg.br', 'whois.nic.br', 'No match'),
('pro.br', 'whois.nic.br', 'No match'),
('psc.br', 'whois.nic.br', 'No match'),
('psi.br', 'whois.nic.br', 'No match'),
('pt', 'whois.ripe.net', 'No match for'),
('qh.cn', 'whois.cnnic.net.cn', 'No entries found'),
('qsl.br', 'whois.nic.br', 'No match'),
('rec.br', 'whois.nic.br', 'No match'),
('ro', 'whois.ripe.net', 'No entries found'),
('ru', 'whois.ripn.ru', 'No entries found'),
('sc.cn', 'whois.cnnic.net.cn', 'No entries found'),
('sd.cn', 'whois.cnnic.net.cn', 'No entries found'),
('se', 'whois.nic-se.se', 'No data found'),
('se.com', 'whois.nomination.net', 'No match for'),
('se.net', 'whois.nomination.net', 'No match for'),
('sg', 'whois.nic.net.sg', 'NO entry found'),
('sh', 'whois.nic.sh', 'No match for'),
('sh.cn', 'whois.cnnic.net.cn', 'No entries found'),
('si', 'whois.arnes.si', 'No entries found'),
('sk', 'whois.ripe.net', 'no entries found'),
('slg.br', 'whois.nic.br', 'No match'),
('sm', 'whois.ripe.net', 'no entries found'),
('sn.cn', 'whois.cnnic.net.cn', 'No entries found'),
('srv.br', 'whois.nic.br', 'No match'),
('st', 'whois.nic.st', 'No entries found'),
('su', 'whois.ripe.net', 'No entries found'),
('sx.cn', 'whois.cnnic.net.cn', 'No entries found'),
('tc', 'whois.adamsnames.tc', 'is not registered'),
('tel.tr', 'whois.nic.tr', 'Not found in database'),
('th', 'whois.nic.uk', 'No entries found'),
('tj.cn', 'whois.cnnic.net.cn', 'No entries found'),
('tm', 'whois.nic.tm', 'No match for'),
('tmp.br', 'whois.nic.br', 'No match'),
('tn', 'whois.ripe.net', 'No entries found'),
('to', 'whois.tonic.to', 'No match'),
('trd.br', 'whois.nic.br', 'No match'),
('tur.br', 'whois.nic.br', 'No match'),
('tv', 'whois.nic.tv', 'MAXCHARS:75'),
('tv.br', 'whois.nic.br', 'No match'),
('tw', 'whois.twnic.net', 'NO MATCH TIP'),
('tw.cn', 'whois.cnnic.net.cn', 'No entries found'),
('ua', 'whois.ripe.net', 'No entries found'),
('uk', 'whois.thnic.net', 'No match for'),
('uk.com', 'whois.nomination.net', 'No match for'),
('uk.net', 'whois.nomination.net', 'No match for'),
('us', 'whois.nic.us', 'Not found'),
('va', 'whois.ripe.net', 'No entries found'),
('vet.br', 'whois.nic.br', 'No match'),
('vg', 'whois.adamsnames.tc', 'is not registered'),
('wattle.id.au', 'whois.aunic.net', 'No Data Found'),
('web.tr', 'whois.nic.tr', 'Not found in database'),
('ws', 'whois.worldsite.ws', 'No match for'),
('xj.cn', 'whois.cnnic.net.cn', 'No entries found'),
('xz.cn', 'whois.cnnic.net.cn', 'No entries found'),
('yn.cn', 'whois.cnnic.net.cn', 'No entries found'),
('yu', 'whois.ripe.net', 'No entries found'),
('za', 'whois.frd.ac.za', 'No match for'),
('zj.cn', 'whois.cnnic.net.cn', 'No entries found'),
('zlg.br', 'whois.nic.br', 'No match'),
('co.nr', '', ''),
('co.nz', '', ''),
('tk', '', ''),
('in', '', ''),
('gov', '', ''),
('hr', '', ''),
('fm', 'n/a', 'n/a'),
('com.gr', '', ''),
('net.gr', '', ''),
('org.gr', '', ''),
('edu.gr', '', '');