Parse the PHP version to obtain the redirected address (code)_PHP tutorial

//取重定向的地址
 class RedirectUrl{
     //地址
     var $url;
     //初始化地址
     function RedirectUrl($url){
         $this->url = $url;
     }
     /**
* get_redirect_url()
* Get the redirected address
* *
* @param string $url
* @return string
*/
     private function get_redirect_url($url){
         $redirect_url = null;

         $url_parts = @parse_url($url);
         if (!$url_parts) return false;
         if (!isset($url_parts['host'])) return false; //can't process relative URLs
         if (!isset($url_parts['path'])) $url_parts['path'] = '/';

         $sock = fsockopen($url_parts['host'], (isset($url_parts['port']) ? (int)$url_parts['port'] : 80), $errno, $errstr, 30);
         if (!$sock) return false;

         $request = "HEAD " . $url_parts['path'] . (isset($url_parts['query']) ?'?'.$url_parts['query'] : '') . " HTTP/1.1rn";
         $request .= 'Host: ' . $url_parts['host'] . "rn";
         $request .= "Connection: Closernrn";
         fwrite($sock, $request);
         $response = '';
         while(!feof($sock)) $response .= fread($sock, 8192);
         fclose($sock);

         if (preg_match('/^Location: (.+?)$/m', $response, $matches)){
             return trim($matches[1]);
         } else {
             return false;
         }
     }

     /**
* get_all_redirects()
* Get all redirect addresses
* *
* @param string $url
* @return array
*/
     private function get_all_redirects($url){
         $redirects = array();
         while ($newurl = $this->get_redirect_url($url)){
             if (in_array($newurl, $redirects)){
                 break;
             }
             $redirects[] = $newurl;
             $url = $newurl;
         }
         return $redirects;
     }

     /**
* get_final_url()
* Get the actual address
* *
* @param string $url
* @return string
*/
     function get_final_url(){
         $redirects = $this->get_all_redirects($this->url);

         if (count($redirects)>0){
             return array_pop($redirects);
         } else {
             return $this->url;
         }
     }
 }

/**
* get_show_pic
* Get the address of the final image to be displayed
*
* @param string $url
* @return string
*/
function get_show_pic($url,$noimg ='noimg.gif',$newimg="http://special.ku6img.com/projects/2010/ d-color/images/slt-1.jpg"){
$obj = new RedirectUrl($url);

$realurl = $obj->get_final_url();

if(strpos($realurl,$noimg)>0){
return $newimg;
}
return $url;
}
//Reference
echo "< ;img src='".get_show_pic("http://i2.ku6img.com/encode/picpath/2010/12/9/14/1294948410019/5.jpg")."'/>";
?>