public function readFolder($folderPath, $fileFilter = '*')
    {
        // make sure folderPath ends with '/'
        if ('/' !== substr($folderPath, -1)) {
            $folderPath .= '/';
        }
        $searchPattern = $folderPath.$fileFilter;
        $fileList = @glob($searchPattern, GLOB_MARK | GLOB_ERR);
        if (false === $fileList) {
            return [];
        }

        return $fileList;
    }