private function addHeadersForOptionsRequests()
    {
        // header for preflight cache expiry
        $maxAge = self::MAX_AGE;
        if (isset($this->options[self::HEADER_MAX_AGE])) {
            $maxAge = intval($this->options[self::HEADER_MAX_AGE]);
        }
        @header(self::HEADER_MAX_AGE.': '.$maxAge);

        // header for allowed request headers in cross origin requests
        $allowedHeaders = self::$allowedHeaders;
        if (isset($this->options[self::HEADER_ALLOW_HEADERS])) {
            $allowedHeaders = (array)$this->options[self::HEADER_ALLOW_HEADERS];
        }
        @header(self::HEADER_ALLOW_HEADERS.':'.implode(',', $allowedHeaders));

        // header for allowed HTTP methods in cross orgin requests
        $allowedMethods = self::$allowedMethods;
        if (isset($this->options[self::HEADER_ALLOW_METHODS])) {
            $allowedMethods = (array)$this->options[self::HEADER_ALLOW_METHODS];
        }
        @header(self::HEADER_ALLOW_METHODS.':'.implode(',', $allowedMethods));
    }