php获取301跳转URL

/** * get_redirect_url() * Gets the address that the provided URL redirects to, * or FALSE if there's no redirect.  * * @param string $url * @return string */function get_redirect_url($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, $matches)){        if ( substr($matches[1], 0, 1) == "/" )            return $url_parts['scheme'] . "://" . $url_parts['host'] . trim($matches[1]);        else            return trim($matches[1]);      } else {        return false;    }     }/** * get_all_redirects() * Follows and collects all redirects, in order, for the given URL.  * * @param string $url * @return array */function get_all_redirects($url){    $redirects = array();    while ($newurl = get_redirect_url($url)){        if (in_array($newurl, $redirects)){            break;        }        $redirects[] = $newurl;        $url = $newurl;    }    return $redirects;}