How do I work with a collection that is a child of a collection in Laravel 5.7?

Question

How can I return the child collection of a collection in Laravel 5.7? I have a Laravel collection that itself contains a collection. When I return the parent collection through my api, there is clearly a "children" object, but when I try to return the "children" object it is null.

Relevant collection code:

$item =  [
  'id' => $this->id,
  ...
  $this->mergeWhen($this->type === Item::[type], [
     ...
     'children' => [type]::collection($this->[prop])
  ]),
...
return $item;
];

Relevant api controller code:

$itemsQuery = $[parent_type]->items()->topLevel()->withAll()->ordered()->get();
$items = [type]::collection($itemsQuery);

$return_array = [];

foreach ($items as $item)
{         
  array_push($return_array, $item);  
}    

return $return_array;

This returns what I would expect.

"data": {
    "id": [guid],
    ...
    "children": [
     {
       "id": [guid],
       ...
     }
  ]
}

but when I change it to

$itemsQuery = $[parent_type]->items()->topLevel()->withAll()->ordered()->get();
$items = [type]::collection($itemsQuery);

$return_array = [];

foreach ($items as $item)
{         
  array_push($return_array, $item->children);  
}    

return $return_array;

I get

"data": null

Answer 1

Try this :

...

$return_array = collect();

foreach ($items as $item)
{         
  $return_array->push($item->children); 
}    

return $return_array->toArray();

Answer 2

有一个collect()助手，不确定它是否会帮助您，但是您可以通过这种方式将基本数组转换为集合。