public static function lowerFirst(string $str, string $encoding = null) : string
    {
        $encoding = $encoding ?: utils\Str::encoding($str);

        // Lowercase the first character and append the remainder.
        return mb_strtolower(mb_substr($str, 0, 1, $encoding), $encoding) . mb_substr($str, 1, null, $encoding);
    }