Illuminate\Support\Collection::transform PHP Method

    public function transform(callable $callback)
    {
        $this->items = $this->map($callback)->all();
        return $this;
    }

 /**
  * @param array|Arrayable $data
  * @return $this
  */
 public function fill($data)
 {
     $this->data = new Collection($data);
     $this->data->transform(function ($record) {
         return $record instanceof Arrayable ? $record->toArray() : $record;
     });
     return $this;
 }