public function length($val, $lower, $upper, $id, $name = null) {
        if (strlen($val) < $lower) {
            if (is_null($name))
                $name = ucwords($id);
            $this->add($id, "$name must be at least $lower characters.");
            return false;
        }
        elseif (strlen($val) > $upper) {
            if (is_null($name))
                $name = ucwords($id);
            $this->add($id, "$name cannot be more than $upper characters long.");
            return false;
        }

        return true;
    }