public static function isOneOf($input, array $values, $caseInsensitive = false, $returnIndex = false)
    {
        if (is_null($input)) {
            return false;
        }

        foreach ($values as $index => $str) {
            if (static::equals($input, $str, $caseInsensitive)) {
                return ($returnIndex) ? $index : true;
            }
        }

        return false;
    }