RBL check script

gistfile1.php

<?php

$rbls = [
	'b.barracudacentral.org',
	'cbl.abuseat.org',
	'http.dnsbl.sorbs.net',
	'misc.dnsbl.sorbs.net',
	'socks.dnsbl.sorbs.net',
	'web.dnsbl.sorbs.net',
	'dnsbl-1.uceprotect.net',
	'dnsbl-3.uceprotect.net',
	'sbl.spamhaus.org',
	'zen.spamhaus.org',
	'psbl.surriel.com',
	'dnsbl.njabl.org',
	'rbl.spamlab.com',
	'noptr.spamrats.com',
	'cbl.anti-spam.org.cn',
	'dnsbl.inps.de',
	'httpbl.abuse.ch',
	'korea.services.net',
	'virus.rbl.jp',
	'wormrbl.imp.ch',
	'rbl.suresupport.com',
	'ips.backscatterer.org',
	'opm.tornevall.org',
	'multi.surbl.org',
	'tor.dan.me.uk',
	'relays.mail-abuse.org',
	'rbl-plus.mail-abuse.org',
	'access.redhawk.org',
	'rbl.interserver.net',
	'bogons.cymru.com',
	'bl.spamcop.net',
	'dnsbl.sorbs.net',
	'dul.dnsbl.sorbs.net',
	'smtp.dnsbl.sorbs.net',
	'spam.dnsbl.sorbs.net',
	'zombie.dnsbl.sorbs.net',
	'dnsbl-2.uceprotect.net',
	'pbl.spamhaus.org',
	'xbl.spamhaus.org',
	'bl.spamcannibal.org',
	'ubl.unsubscore.com',
	'combined.njabl.org',
	'dyna.spamrats.com',
	'spam.spamrats.com',
	'cdl.anti-spam.org.cn',
	'drone.abuse.ch',
	'dul.ru',
	'short.rbl.jp',
	'spamrbl.imp.ch',
	'virbl.bit.nl',
	'dsn.rfc-ignorant.org',
	'dsn.rfc-ignorant.org',
	'netblock.pedantic.org',
	'ix.dnsbl.manitu.net',
	'rbl.efnetrbl.org',
	'blackholes.mail-abuse.org',
	'dnsbl.dronebl.org',
	'db.wpbl.info',
	'query.senderbase.org',
	'bl.emailbasura.org',
	'combined.rbl.msrbl.net',
	'multi.uribl.com',
	'black.uribl.com',
	'cblless.anti-spam.org.cn',
	'cblplus.anti-spam.org.cn',
	'blackholes.five-ten-sg.com',
	'sorbs.dnsbl.net.au',
	'rmst.dnsbl.net.au',
	'dnsbl.kempt.net',
	'blacklist.woody.ch',
	'rot.blackhole.cantv.net',
	'virus.rbl.msrbl.net',
	'phishing.rbl.msrbl.net',
	'images.rbl.msrbl.net',
	'spam.rbl.msrbl.net',
	'spamlist.or.kr',
	'dnsbl.abuse.ch',
	'bl.deadbeef.com',
	'ricn.dnsbl.net.au',
	'forbidden.icm.edu.pl',
	'probes.dnsbl.net.au',
	'ubl.lashback.com',
	'ksi.dnsbl.net.au',
	'uribl.swinog.ch',
	'bsb.spamlookup.net',
	'dob.sibl.support-intelligence.net',
	'url.rbl.jp',
	'dyndns.rbl.jp',
	'omrs.dnsbl.net.au',
	'osrs.dnsbl.net.au',
	'orvedb.aupads.org',
	'relays.nether.net',
	'relays.bl.gweep.ca',
	'relays.bl.kundenserver.de',
	'dialups.mail-abuse.org',
	'rdts.dnsbl.net.au',
	'duinv.aupads.org',
	'dynablock.sorbs.net',
	'residential.block.transip.nl',
	'dynip.rothen.com',
	'dul.blackhole.cantv.net',
	'mail.people.it',
	'blacklist.sci.kun.nl',
	'all.spamblock.unit.liu.se',
	'spamguard.leadmon.net',
    'csi.cloudmark.com',
];

$ip          = '';
$rev         = join('.', array_reverse(explode('.', trim($ip))));
$i           = 1;
$rbl_count   = count($rbls);
$listed_rbls = [];

foreach ($rbls as $rbl)
{
    printf('Checking %s, %d of %d... ', $rbl, $i, $rbl_count);
    $lookup = sprintf('%s.%s', $rev, $rbl);

    $listed = gethostbyname($lookup) !== $lookup;

    printf('[%s]%s', $listed ? 'LISTED' : 'OK', PHP_EOL);

    if ( $listed )
    {
        $listed_rbls[] = $rbl;
    }

    $i++;
}

printf('%s listed on %d of %d known blacklists%s', $ip, count($listed_rbls), $rbl_count, PHP_EOL);

if ( ! empty($listed_rbls) )
{
    printf('%s listed on %s%s', $ip, join(', ', $listed_rbls), PHP_EOL);
}

Hi can you update the code to support IPv6 also ...?