PHP

Merging Two Laravel Collections keeping the original keys

$material_grp1 = Batch::findOrFail($batch_id)->batchdetails->mapWithKeys(function($item)  {                
            return [
                $item->material_id => $item
            ];
        });;
         $material_grp2 = Batch::with('productoutput.productoutputdetails.packsizes')
                            ->find($batch_id)->productoutput->productoutputdetails
                            ->mapWithKeys(function($item)  {                
            return [
                $item->packsizes->material_id => $item
            ];
        });
         $material_grp = $material_grp1->union($material_grp2);