add new element in laravel collection object

I want to add new element in $items array, I don't want to use joins for certain reasons.

$items = DB::select(DB::raw('SELECT * FROM items WHERE items.id = '.$id.'  ;'));
        foreach($items as $item){
            $product = DB::select(DB::raw(' select * from product
                   where product_id = '. $id.';' ));

            $item->push($product);
        }

what should i do, please help, thnx in advance

via Chebli Mohamed