使用codeigniter显示模型类别

Question

我编写了一个模型函数来使用codeigniter获取类别及其子类别。我想在一个下拉列表中显示完整的层次结构。

Category
     sub1
       sub1.1
       sub1.2
     sub2
     sub3
        sub3.1
           sub3.1.1
        and so on.


MY model

     public function getCategoryTreeForParentId($parent_id = 0) {

      $categories = array();
      $this->db->from('jil_category');
      $this->db->where('ctg_parent', $parent_id);
      $result = $this->db->get()->result();
      foreach ($result as $mainCategory) {
        $category = array();
        $category['id'] = $mainCategory->ctg_id;
        $category['name'] = $mainCategory->ctg_name;
        $category['parent_id'] = $mainCategory->ctg_parent;
        $category['sub_categories'] = $this->getCategoryTreeForParentId($category['id']);
        $categories[$mainCategory->ctg_id] = $category;
      }
      return $categories;
    }