Regex generator for valid TLDs

<?php
	/* Regex generator for valid TLDs - By MrJack*/
	$txt = file_get_contents('http://data.iana.org/TLD/tlds-alpha-by-domain.txt');
	$tlds = preg_split('/\s+/', $txt);
	$valid_tld = array();
	foreach($tlds as $tld){
		if (! preg_match('/[^a-z]+/i', $tld, $matches)){
			if(strlen($tld) > 3){
				array_push($valid_tld, strtolower($tld));
			}
		}
	}
	echo implode("|",$valid_tld)."|[a-z]{2}";