Laravel显示层次结构类别

Question

我有产品表：

id | name
-----------
 1 | orange
 2 | ampalaya
 3 | mango
 4 | pork

和类别表：

id | parent_id | name
----------------------
 1 |    0      | fruits
 2 |    0      | vegetables
 3 |    1      | yellow fruits
 4 |    3      | small fruits
 5 |    2      | green vegies
 6 |    0      | meat
 7 |    0      | shape
 8 |    7      | circle
 9 |    7      | oblong

我有product_categories表：

product_id | category _id
--------------------------
    1      |    1
    1      |    4
    3      |    1
    3      |    3
    3      |    4
    2      |    2
    2      |    5
    4      |    6
    1      |    7
    1      |    8
    3      |    7
    3      |    9

我的问题是如何显示每种产品的类别？我想要这个输出：

product name |  categories  
---------------------------------------------------------------------
mango        |  fruits > yellow fruits > small fruits , shape > oblong
orange       |  fruits > small fruits , shape > circle
ampalaya     |  vegetables > green vegies
pork         |  meat

我在我的模型上试过这个功能：

   public static function listCategories($product_id)
   {
       $product_cats = DB::table('product_categories as pc')
                   ->join('categories as c','c.id','=','pc.category_id')
                   ->where('pc.product_id',$product_id)
                   ->select('c.id','c.parent_id','c.name','pc.category_id')
                   ->get();
       $categories = DB::table('categories')->get();

       $category = array(
           'categories' => array(),
           'parent_cats' => array()
       );

       foreach($categories as $cat) {
           $category['categories'][$cat->id] = $cat;
           $category['parent_cats'][$cat->parent_id][] = $cat->id;
       }

       return Category::list_categories(0,$category,$product_cats);
  }

public static function list_categories($parent, $category, $product_cats)
{
    $html = "";
    $ctr = count($product_cats) - 1;
    if (isset($category['parent_cats'][$parent])) {
        foreach ($category['parent_cats'][$parent] as $cat_id) {
            if (!isset($category['parent_cats'][$cat_id])) {
                foreach($product_cats as $key1 => $cats) {
                    if($cat_id == $cats->category_id) {
                        if($key1 == $ctr){
                           $html .= $category['categories'][$cat_id]->name;
                        } else {
                           $html .= $category['categories'][$cat_id]->name.', ';
                        }
                    }
                    $ctr--;
                }
            }
            if (isset($category['parent_cats'][$cat_id])) {
                foreach($product_cats as $key => $cats) {
                    foreach ($category['parent_cats'][$cat_id] as $cat_ids) {
                        if($cat_ids == $cats->parent_id) {
                            $html .= $category['categories'][$cat_ids]->name.' >> ';
                        }
                    }
                    if($cat_id == $cats->category_id) {
                        if($key == $ctr) {
                           $html .= $category['categories'][$cat_id]->name;
                        } else {
                           $html .= $category['categories'][$cat_id]->name.', ';
                        }
                    }
                }
                $ctr--;
                $html .= Category::list_categories($cat_id, $category, $product_cats);
            }
        }
    }
    return $html;
}

在我的显示/查看页面上：

@foreach($products as $prod)
    <tr>
        <td> {!! $prod->name !!}</td>
        <td> {!! Category::listCategories($prod->id) !!}</td>
    </tr>
@endforeach

在我的控制器上：

$data['products'] = DB::table('products')->get();