PHP 获取顶级域名

<?php
function get_domain() {
	$host = $_SERVER['HTTP_HOST'];
	$host = strtolower($host);
	if(strpos($host,'/')!==false){
		$parse = @parse_url($host);
		$host = $parse['host']; }
		$topleveldomaindb=array('com','edu','gov','int','mil','net','org','biz','info','pro','name','museum','coop','aero','xxx','idv','mobi','cc','me'); $str='';
		foreach($topleveldomaindb as $v){
		$str.=($str ? '|' : '').$v;
	}
	$matchstr="[^\.]+\.(?:(".$str.")|\w{2}|((".$str.")\.\w{2}))$";
	if(preg_match("/".$matchstr."/ies",$host,$matchs)){
		$domain=$matchs['0'];
	}else{
		$domain=$host;
	}
	return $domain;
}
echo get_domain();
?>

效果图：