protected function updateChildren()
    {
        $children = $this->manager->getChildren($this->item->name);
        $childrenNames = array_keys($children);

        if (is_array($this->children)) {
            // remove children that
            foreach (array_diff($childrenNames, $this->children) as $item) {
                $this->manager->removeChild($this->item, $children[$item]);
            }
            // add new children
            foreach (array_diff($this->children, $childrenNames) as $item) {
                $this->manager->addChild($this->item, $this->manager->getItem($item));
            }
        } else {
            $this->manager->removeChildren($this->item);
        }
    }