public function getBasicResponse()
    {
        // Default the basic response
        if ($this->basicResponse === null) {
            $this->basicResponse = function () {
                if (headers_sent()) {
                    throw new RuntimeException('Attempting basic auth after headers have already been sent.');
                }

                header('WWW-Authenticate: Basic');
                header('HTTP/1.0 401 Unauthorized');

                echo 'Invalid credentials.';
                exit;
            };
        }

        $response = $this->basicResponse;

        return $response();
    }