public static function camelize($string, $separator = null, $preserveWhiteSpace = false, $isKey = false)
    {
        empty($separator) && $separator = ['_', '-'];

        $_newString = ucwords(str_replace($separator, ' ', $string));

        if (false !== $isKey) {
            $_newString = lcfirst($_newString);
        }

        return (false === $preserveWhiteSpace ? str_replace(' ', null, $_newString) : $_newString);
    }