public function clearCacheFiles()
    {
        if (false === $this->cache) {
            return;
        }

        foreach (new RecursiveIteratorIterator(new RecursiveDirectoryIterator($this->cache), RecursiveIteratorIterator::LEAVES_ONLY) as $file) {
            if ($file->isFile()) {
                @unlink($file->getPathname());
            }
        }
    }