protected function toBytes($str){
        $val = substr(trim($str), 0, strlen($str)-1);
        $last = strtolower($str[strlen($str)-1]);
        switch($last) {
            case 'g': $val *= 1024;
            case 'm': $val *= 1024;
            case 'k': $val *= 1024;
        }
        return $val;
    }