            $digits = $integer = substr($integer, 1); // rm unnecessary plus
        } else {
            $digits = $integer;
        }

        // test if it's numeric
        if (!ctype_digit($digits)) return false;

        // perform scope tests
        if (!$this->zero     && $integer == 0) return false;
        if (!$this->positive && $integer > 0) return false;
        if (!$this->negative && $integer < 0) return false;

        return $integer;

    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.