public static function swapCase($inputString)
    {
        if (true === StringUtils::isEmpty($inputString)) {
            return $inputString;
        }

        $buffer = \str_split($inputString);
        $length = \count($buffer);

        for ($i = 0; $i < $length; ++$i) {
            $char = $buffer[$i];

            if (true === \ctype_upper($char)) {
                $buffer[$i] = StringUtils::lowerCase($char);
            } elseif (true === \ctype_lower($char)) {
                $buffer[$i] = StringUtils::upperCase($char);
            }
        }

        return \implode($buffer);
    }