protected function validator($input)
    {
        $this->checkValue($input);

        if ($this->hasErrors()) {
            return '';
        }

        if (!$input) {
            if ($this->mandatory) {
                $this->addError(sprintf($GLOBALS['TL_LANG']['ERR']['mandatory'], $this->strLabel));
            }

            return '';
        } elseif (false === strpos($input, ',')) {
            return $this->multiple ? [(int) $input] : (int) $input;
        }
        $arrValue = array_map('intval', array_filter(explode(',', $input)));

        return $this->multiple ? $arrValue : $arrValue[0];
    }