protected function setCacheHeaders($lastModified, $file, $hit)
    {
        //  Set some flags
        $this->cacheHeadersSet          = true;
        $this->cacheHeadersMaxAge       = 31536000; // 1 year
        $this->cacheHeadersLastModified = $lastModified;
        $this->cacheHeadersExpires      = time() + $this->cacheHeadersMaxAge;
        $this->cacheHeadersFile         = $file;
        $this->cacheHeadersHit          = $hit ? 'HIT' : 'MISS';

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

        header('Cache-Control: max-age=' . $this->cacheHeadersMaxAge . ', must-revalidate', true);
        header('Last-Modified: ' . date('r', $this->cacheHeadersLastModified), true);
        header('Expires: ' . date('r', $this->cacheHeadersExpires), true);
        header('ETag: "' . md5($this->cacheHeadersFile) . '"', true);
        header('X-CDN-CACHE: ' . $this->cacheHeadersHit, true);
    }