php中取得URL的根域名的代码

<?php 
/** 
* 取得根域名 
* 
* @author lonely 
* @create 2011-3-11 
* @version 0.1 
* @lastupdate lonely 
* @package Sl 
*/ 
class Sl_RootDomain{ 
private static $self; 
private $domain=null; 
private $host=null; 
private $state_domain; 
private $top_domain; 
/** 
* 取得域名分析实例 
* Enter description here ... 
*/ 
public static function instace(){ 
if(!self::$self) 
self::$self=new self(); 
return self::$self; 
} 
private function __construct(){ 
$this->state_domain=array( 
'al','dz','af','ar','ae','aw','om','az','eg','et','ie','ee','ad','ao','ai','ag','at','au','mo','bb','pg','bs','pk','py','ps','bh','pa','br','by','bm','bg','mp','bj','be','is','pr','ba','pl','bo','bz','bw','bt','bf','bi','bv','kp','gq','dk','de','tl','tp','tg','dm','do','ru','ec','er','fr','fo','pf','gf','tf','va','ph','fj','fi','cv','fk','gm','cg','cd','co','cr','gg','gd','gl','ge','cu','gp','gu','gy','kz','ht','kr','nl','an','hm','hn','ki','dj','kg','gn','gw','ca','gh','ga','kh','cz','zw','cm','qa','ky','km','ci','kw','cc','hr','ke','ck','lv','ls','la','lb','lt','lr','ly','li','re','lu','rw','ro','mg','im','mv','mt','mw','my','ml','mk','mh','mq','yt','mu','mr','us','um','as','vi','mn','ms','bd','pe','fm','mm','md','ma','mc','mz','mx','nr','np','ni','ne','ng','nu','no','nf','na','za','aq','gs','eu','pw','pn','pt','jp','se','ch','sv','ws','yu','sl','sn','cy','sc','sa','cx','st','sh','kn','lc','sm','pm','vc','lk','sk','si','sj','sz','sd','sr','sb','so','tj','tw','th','tz','to','tc','tt','tn','tv','tr','tm','tk','wf','vu','gt','ve','bn','ug','ua','uy','uz','es','eh','gr','hk','sg','nc','nz','hu','sy','jm','am','ac','ye','iq','ir','il','it','in','id','uk','vg','io','jo','vn','zm','je','td','gi','cl','cf','cn','yr' 
); 
$this->top_domain=array('com','arpa','edu','gov','int','mil','net','org','biz','info','pro','name','museum','coop','aero','xxx','idv','me','mobi'); 
$this->url=$_SERVER['HTTP_HOST']; 
} 
/** 
* 设置URL 
* Enter description here ... 
* @param string $url 
*/ 
public function setUrl($url=null){ 
$url=$url?$url:$this->url; 
if(empty($url))return $this; 
if(!preg_match("/^http::/is", $url)) 
$url="http://".$url; 
$url=parse_url(strtolower($url)); 
$urlarr=explode(".", $url['host']); 
$count=count($urlarr); 
if ($count<=2){ 
$this->domain=array_pop($url); 
}else if ($count>2){ 
$last=array_pop($urlarr); 
$last_1=array_pop($urlarr); 
if(in_array($last, $this->top_domain)){ 
$this->domain=$last_1.'.'.$last; 
$this->host=implode('.', $urlarr); 
}else if (in_array($last, $this->state_domain)){ 
$last_2=array_pop($urlarr); 
if(in_array($last_1, $this->top_domain)){ 
$this->domain=$last_2.'.'.$last_1.'.'.$last; 
$this->host=implode('.', $urlarr); 
}else{ 
$this->host=implode('.', $urlarr).$last_2; 
$this->domain=$last_1.'.'.$last; 
} 
} 
} 
return $this; 
} 
/** 
* 取得域名 
* Enter description here ... 
*/ 
public function getDomain(){ 
return $this->domain; 
} 
/** 
* 取得主机 
* Enter description here ... 
*/ 
public function getHost(){ 
return $this->host; 
} 
} 
?>