php 版获取重定向后的地址

<?php
//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()
     * 取重定向的地址
     *
     * @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/1.1\r\n";
        $request .= 'Host: ' . $url_parts['host'] . "\r\n";
        $request .= "Connection: Close\r\n\r\n";
        fwrite($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()
     * 取所有重定向地址
     *
     * @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()
     * 取实际地址
     * 
     * @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
 * 取最终要显示的图片地址
 *
 * @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;
}
//参考
echo "<img src='".get_show_pic("http://i2.ku6img.com/encode/picpath/2010/12/9/14/1294948410019/5.jpg")."'/>";
?>

<?php
//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()
     * 取重定向的地址
     *
     * @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/1.1\r\n";
        $request .= 'Host: ' . $url_parts['host'] . "\r\n";
        $request .= "Connection: Close\r\n\r\n";
        fwrite($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()
     * 取所有重定向地址
     *
     * @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()
     * 取实际地址
     * 
     * @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
 * 取最终要显示的图片地址
 *
 * @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;
}
//参考
echo "<img src='".get_show_pic("http://i2.ku6img.com/encode/picpath/2010/12/9/14/1294948410019/5.jpg")."'/>";
?>