public function addElement(MenuElement $menuElement, $isStartElement = false)
    {
        if (!in_array($menuElement, $this->elements, true)) {
            array_push($this->elements, $menuElement);
            if ($isStartElement) {
                // new start element
                $this->setStartElement($menuElement);
            } else {
                // additional element - set invisible
                $menuElement->getControl()
                            ->setVisible(false);
            }
        }
        return $this;
    }