Prepare an item at the start of each item in the Laravel Eloquent Collection

I have a collection like this

[
  {
    "objective_id": "26",
    "objective_weight": "50.00",
    "objective_description": "This is first strategic objective",
    "actions": [
    ]
  },
  {
    "objective_id": "27",
    "objective_weight": "12.00",
    "objective_description": "This second strategic objective",
    "actions": [
    ]
  },

]

      

        
        
        
      

    

Now I want to add an item for each item in the collection. eg:

[
  {
    "foo" : "bar"
    "objective_id": "26",
    "objective_weight": "50.00",
    "objective_description": "This is first strategic objective",
    "actions": [
    ...
    .....

      

        
        
        
      

    

I tried the prepend()

Eloquent method but couldn't.

$new = $objectives->map(function($objective) {
    return $objective->get()->prepend('hello', 'world');
});

return $new;