error in update attribute contain '-' in laravel

I'm having trouble when update attribute contain '-' :

public function update(Request $request, $id)
    {
      $qustiondata = qustionmodel::find($id);
         $qustiondata->name-man = $request->get('name-man');/*problem expression is not assignable constant reference*/
         $qustiondata->type = $request->get('type');/*no problem here*/
    }

via Chebli Mohamed