Array push does not push the whole items of an array

I am reading a json file like this:

 $path = storage_path() . "/userexam.json"; 
 $json = json_decode(file_get_contents($path), true); 

 foreach($json as $js){
       dd($js);
 }

And the result of dd($js) which shows every single element of json goes like this:

array:13 [▼
  "_id" => "d4466d06-3d47-41c4-aa5e-664752d84004"
  "user" => "0123456789"
  "exam" => "First Exam"
  "total_time_in_minute" => 8640
  "number_of_question" => 17
  "start_time" => array:1 [▶]
  "questions" => array:17 [▶]
  "last_question" => 10
  "is_finished" => false
  "result" => null
  "updated_at" => array:1 [▶]
  "created_at" => array:1 [▶]
  "score" => null
]

Now I want to push these elements into a single array.

So I did this:

$array_results = [];
foreach($json as $js){
    array_push($array_results, $js);
}
dd($array_results);

But now the results of dd($array_results) goes like this:

As you can see it does not show the sub-arrays start_time, questions, updated_at and created_at and only a count number exists.

So how can I push the whole arrays into a new one while they're sub-arrays also exist in the new array?