public function sortByKeys( \Closure $callback )
	{
		$items = $this->items;
		uksort($items, $callback);
		return new static($items);
	}
public function sortByKeys( \Closure $callback )
	{
		$items = $this->items;
		uksort($items, $callback);
		return new static($items);
	}
public function sortByKeys ( \ Closure $ callback ) { $ items = $ this -> items ; uksort ( $ items , $ callback ) ; return new static ( $ items ) ; }
Sort an collection by keys using a user-defined comparison function

@param \Closure $callback
@return static
Sort an collection by keys using a user - defined comparison function