Online PHP editor | refs for JkNf2

<?php $testArray = array( 'sub1.sub2.example.co.uk', 'sub1.example.com', 'example.com', 'sub1.sub2.sub3.example.co.uk', 'sub1.sub2.sub3.example.com', 'sub1.sub2.example.com' ); foreach($testArray as $k => $v) { echo $k." => ".extract_domain($v)."\n"; } function extract_domain($domain) { if(preg_match("/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i", $domain, $matches)) { return $matches['domain']; } else { return $domain; } } function extract_subdomains($domain) { $subdomains = $domain; $domain = extract_domain($subdomains); $subdomains = rtrim(strstr($subdomains, $domain, true), '.'); return $subdomains; }