private function getHttpHeadersAsString($headers)
    {
        if (count($headers) == 0) {
            return '';
        }

        $max = max(array_map('strlen', array_keys($headers))) + 1;
        $content = '';
        ksort($headers);
        foreach ($headers as $name => $values) {
            foreach ($values as $value) {
                $content .= sprintf("%-{$max}s %s\r\n", $this->beautifyHeaderName($name).':', $value);
            }
        }

        return $content;
    }