Laravel collection chunk() method

I'm building an application on Laravel where I'm trying to store 100 datasets into DynamoDB, after reading the documentation DynamoDB can only accept 25 records at a time so I'm trying to store this in chunks of 25.

For this I tried to use Laravel's collection method, but somehow the format is getting changed and I'm getting DynamoDB error SerializationException, here's my code:

$posts = collect($request->posts)->map(function ($items){
  //... transforming the array and returning it
})->chunk(25)

foreach($posts->all() as $chunk) {         
    Post::batchPutItem(collect($chunk)->toArray());
}


return response()->json(['data' => $posts], 200);

First 25 records are saved appropriately, I start getting errors from second iteration. When I inspected the data/returned the chunk I found that data gets transformed

As you can see the first chunk is in array, but next chunk becomes object.

I even tried ->chunk(25, true) but no luck.

Any solution or work around to this?

Linked in the comments show the underlying reason. JS handles associative arrays in PHP by converting them to objects, with each index used as an object key. To get around this, you'd need to further map the $posts:

return response()->json(['data' => $posts->map(function ($chunk) {
  return $chunk->values();
  /* or `return array_values($chunk)` if `$chunk` is an Array instead of a Collection */
}], 200);

With a simple dataset of:

$posts = collect([0, 1, 2, 3, 4, 5, 6, 7])->chunk(4);

echo json_encode($posts);
echo json_encode($posts->map(function ($chunk) { 
  return $chunk->values();
});

The first will output what you're seeing:

[[0,1,2,3],{"4":4,"5":5,"6":6,"7":7}]

While the second will output it as you're expecting:

[[0,1,2,3],[4,5,6,7]]

Links for reference:

https://laravel.com/docs/10.x/collections#method-values

https://php.net/manual/en/function.array-values.php