Illuminate\Support\Collection::only PHP Method

    public function only($keys)
    {
        if (is_null($keys)) {
            return new static($this->items);
        }
        $keys = is_array($keys) ? $keys : func_get_args();
        return new static(Arr::only($this->items, $keys));
    }

 /**
  * @param array| string $keys
  *
  * @return FieldInterface[]|Collection
  */
 public function getOnly($keys)
 {
     if (!is_array($keys)) {
         $keys = func_get_args();
     }
     return $this->fields->only($keys);
 }