Laravel casting empty JSON objects as empty arrays on the Illuminate\Http\Request class

[lgrassini]

• Laravel Version: 9.22.1
• PHP Version: 8.0.2
• Database Driver & Version: None

Description:

When sending a POST or PUT request providing JSON data in the body the Illuminate\Http\Request class will cast any empty JSON object as empty array.

Steps To Reproduce:

Create a simple route that will just output the received request:

    Route::post('/test', function (Request $request) {
        return $request;
    });

Send a POST or PUT request to the above created endpoint with a JSON payload containing an empty JSON object:

POST /api/test HTTP/1.1
Accept: application/json
Content-Type: application/json; charset=utf-8
Host: 127.0.0.1:8000
Content-Length: 48

{"order_id":123,"customer_id":321,"products":{}}

The response of that request will be:

{
  "order_id": 123,
  "customer_id": 321,
  "products": []
}

Note how Illuminate\Http\Request is casting "products":{} as "products": [].
We are expecting the empty object products to be casted as it is, an empty JSON object, instead of an empty array.

This is also replicable on Laravel 8.x.
A similar issue was already reported here and closed without solution.

[driesvints]

Requests are decoded as associative arrays. After doing that, there's no way of knowing what was an array and what was an object.