protected function setCacheHeaders($lastModified, $file, $hit)
    {
        //  Set some flags
        $this->cdnCacheHeadersSet          = true;
        $this->cdnCacheHeadersLastModified = $lastModified;
        $this->cdnCacheHeadersExpires      = time() + $this->cdnCacheHeadersMaxAge;
        $this->cdnCacheHeadersFile         = $file;
        $this->cdnCacheHeadersHit          = $hit ? 'HIT' : 'MISS';

        // --------------------------------------------------------------------------

        header('Cache-Control: max-age=' . $this->cdnCacheHeadersMaxAge . ', must-revalidate', true);
        header('Last-Modified: ' . date('r', $this->cdnCacheHeadersLastModified), true);
        header('Expires: ' . date('r', $this->cdnCacheHeadersExpires), true);
        header('ETag: "' . md5($this->cdnCacheHeadersFile) . '"', true);
        header('X-CDN-CACHE: ' . $this->cdnCacheHeadersHit, true);
    }