public function formatBytes($size, $pre = 2)
    {
        $base = log($size) / log(1024);
        $suffix = ['B', 'KB', 'MB', 'GB', 'TB', 'PB'];
        $f_base = floor($base);

        return round(pow(1024, $base - floor($base)), $pre).$suffix[$f_base];
    }