public function humanFileSize($file)
    {
        $size = filesize($file);
        $mod = 1024;
        $units = explode(' ', 'B KB MB GB TB PB');
        for ($i = 0; $size > $mod; ++$i) {
            $size /= $mod;
        }

        return round($size, 2).' '.$units[$i];
    }