private function execute($url, array $headers = array(), $callable = null)
    {
        $curl = curl_init();

        curl_setopt($curl, CURLOPT_URL, $this->fixUrl($url));
        curl_setopt($curl, CURLOPT_HEADER, true);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

        if ($this->getMaxRedirects() > 0) {
            curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
            curl_setopt($curl, CURLOPT_MAXREDIRS, $this->getMaxRedirects());
        }

        if (!empty($headers)) {
            curl_setopt($curl, CURLOPT_HTTPHEADER, $this->fixHeaders($headers));
        }

        if ($callable !== null) {
            call_user_func($callable, $curl);
        }

        if (($response = curl_exec($curl)) === false) {
            $error = curl_error($curl);
            curl_close($curl);

            throw HttpAdapterException::cannotFetchUrl($url, $this->getName(), $error);
        }

        $statusCode = curl_getinfo($curl, CURLINFO_HTTP_CODE);
        $headersSize = curl_getinfo($curl, CURLINFO_HEADER_SIZE);
        $effectiveUrl = curl_getinfo($curl, CURLINFO_EFFECTIVE_URL);

        curl_close($curl);

        $headers = substr($response, 0, $headersSize);
        $body = substr($response, $headersSize);

        return $this->createResponse($statusCode, $url, $headers, $body, $effectiveUrl);
    }