无法使用PHP构建嵌套JSON

Question

I am having trouble getting these arrays to nest properly. I am grabbing all the rows from a SQL database and building an array to output in JSON for my crud app. One category has been easy, but the client now wants subcategories and that's when I hit a major wall. I am trying to nest these subcategories into categories. I can do either, but am failing to get them working together. The following is my PHP code:

while ($row = $query->fetch_assoc()) {
    $categories[$row['category']][] = array(
        $row['subcategory'] => $subcategories[$row['subcategory']][] = array(
            'id'                 => $row['id'],
            'item_name'          => $row['item_name'],
            'description'        => $row['description'],
            'price'              => $row['price'],
        ),
    );
}

foreach ($categories as $key => $value) {
    $category_data[] = array(
        'category'   => $key,
        'category_list' => $value,
    );
}

foreach ($subcategories as $key => $value) {
    $subcategory_data[] = array(
        'subcategory'   => $key,
        'subcategory_list' => $value,
    );
}

When I json_encode($category_data) I get the following JSON:

[
{
    "category": "Beer",
    "category_list": [
        {
            "Draft Beer": {
                "id": "1",
                "item_name": "Yuengling",
                "description": "Lager. Pottstown, Pa. An American classic."
            }
        },
        {
            "Draft Beer": {
                "id": "6",
                "item_name": "Bud Light",
                "description": "American Light Lager"
            }
        },
        {
            "Domestic Bottles": {
                "id": "9",
                "item_name": "Stone IPA",
                "description": "India Pale Ale.<em> Escondido, Colo."
            }
        }
    ]
},
{
    "category": "Wine",
    "category_list": [...]
}
]

Which might work, but I would like it to join the like keys (ie: Draft Beer) into the same array. It does do that when I json_encode($subcategory_data) as shown below, but its not separated into categories, just the subcategories.

[
{
    "subcategory": "Draft Beer",
    "subcategory_list": [
        {
            "id": "1",
            "item_name": "Yuengling",
            "description": "Lager. Pottstown, Pa."
        },
        {
            "id": "6",
            "item_name": "Bud Light",
            "description": "American Light Lager. Milwaukee, Wisc."
        }
    ]
},
{
    "subcategory": "Red Wine",
    "subcategory_list": [
        {
            "id": "17",
            "item_name": "Kendall-Jackson",
            "description": "Cabernet Sauvignon, 2010."
        },
        {
            "id": "18",
            "item_name": "Sanford",
            "description": "Pinot Noir, 2011. Lompoc, Calif"
        }
    ]
},
{
    "subcategory": "Domestic Bottles",
    "subcategory_list": [
        {
            "id": "9",
            "item_name": "Stone IPA",
            "description": "India Pale Ale. Escondido, Colo."
        },
        {
            "id": "10",
            "item_name": "Blue Moon",
            "description": "Belgian-style Wheat Ale."
        }
    ]
}
]

So my question is why does it merge in the second set of data but not the first. How do I get the subcategory_data into the category_data. Any help id truly appreciated. Below is an example if what I am looking for:

{
    "category_name":"Beer",
    "category_list" : [
        {
            "subcategory_name": "Draft Beer",
            "subcategory_list": [
            {
                "id": "1",
                "item_name": "Yuengling",
                "description": "Lager. Pottstown, Pa."
            },
            {
                "id": "6",
                "item_name": "Bud Light",
                "description": "American Light Lager. Milwaukee, Wisc."
            }
        }
    ]   
},
{
    "category_name":"Wine",
    "category_list" : [
        {
            "subcategory_name": "Red Wine",
            "subcategory_list": [...]
        }
    ]
}

Thanks for looking, I am fairly new to PHP and am relying on my javascript skills.

Answer 1

First, try var_dump($categories). You'll see that you're building a rather weird data structure (you have arrays of 1-element arrays...). The following code will build a simpler structure:

$categories[$row['category']][$row['subcategory']][] = array(
  'id'                 => $row['id'],
  'item_name'          => $row['item_name'],
  'description'        => $row['description'],
  'price'              => $row['price'],
  );

This will serialize to JSON that's probably acceptable as is:

{
  "Beer": {
    "Draft Beer": [
      {
        "id": "1",
        "item_name": "Yuengling",
        "description": "Lager. Pottstown, Pa."
      },
      {
        "id": "6",
        "item_name": "Bud Light",
        "description": "American Light Lager. Milwaukee, Wisc."
      }
    ],
    ...

An additional transformation gets the data in the format you asked for:

foreach ($categories as $category_name => $subcategories) {
  $subcategory_data = array();
  foreach ($subcategories as $subcategory_name => $items) {
    $subcategory_data[] = array(
      'subcategory_name' => $subcategory_name,
      'subcategory_list' => $items
      );
  }
  $category_data[] = array(
    'category_name' => $category_name,
    'category_items' => $subcategory_data
    );                 
}