public function head($url, $timeout = 10)
    {
        $p = parse_url($url);
        if (!isset($p['scheme'])) {
            $p = parse_url($this->absoluteURI($url));
        } elseif ($p['scheme'] != 'http') {
            throw new InvalidArgumentException(
                'Unsupported protocol: '. $p['scheme']
            );
        }

        $port = isset($p['port']) ? $p['port'] : 80;

        if (!$fp = @fsockopen($p['host'], $port, $eno, $estr, $timeout)) {
            throw new HTTP2_Exception("Connection error: $estr ($eno)");
        }

        $path  = !empty($p['path']) ? $p['path'] : '/';
        $path .= !empty($p['query']) ? '?' . $p['query'] : '';

        fputs($fp, "HEAD $path HTTP/1.0\r\n");
        fputs($fp, 'Host: ' . $p['host'] . ':' . $port . "\r\n");
        fputs($fp, "Connection: close\r\n\r\n");

        $response = rtrim(fgets($fp, 4096));
        if (preg_match("|^HTTP/[^\s]*\s(.*?)\s|", $response, $status)) {
            $headers['response_code'] = $status[1];
        }
        $headers['response'] = $response;

        while ($line = fgets($fp, 4096)) {
            if (!trim($line)) {
                break;
            }
            if (($pos = strpos($line, ':')) !== false) {
                $header = substr($line, 0, $pos);
                $value  = trim(substr($line, $pos + 1));

                $headers[$header] = $value;
            }
        }
        fclose($fp);
        return $headers;
    }