public function getResponseStatusCode ()
    {
        if (!$this->_sent) {
            throw new CAS_OutOfSequenceException(
                'Request has not been sent yet. Cannot '.__METHOD__
            );
        }

        if (!preg_match(
            '/HTTP\/[0-9.]+\s+([0-9]+)\s*(.*)/',
            $this->_responseHeaders[0], $matches
        )
        ) {
            throw new CAS_Request_Exception(
                'Bad response, no status code was found in the first line.'
            );
        }

        return intval($matches[1]);
    }