public function toRoman($number)
    {
        $number = (int)$number;
        $roman = '';
        foreach ($this->getRomanValues() as $romanValue => $numberValue) {
            $roman .= str_repeat($romanValue, floor($number / $numberValue));
            $number = $number % $numberValue;
        }
        foreach ($this->getRomanExceptions() as $replaceThis => $withThis) {
            $roman = str_replace($replaceThis, $withThis, $roman);
        }
        return $roman;
    }