Get 30 or 31 days of certain month in carbon

I don't know how I can't find this anywhere on the web.

 public static function months($futureM) {
        $now = Carbon::now();
        $start    = (new DateTime($now->format('Y-m-d')))->modify('first day of this month');
        $end      = (new DateTime(($now->addMonths($futureM))->format('Y-m-d')))->modify('first day of next month');
        $interval = DateInterval::createFromDateString('1 month');
        $period   = new DatePeriod($start, $interval, $end);
        $months = array();
        foreach ($period as $dt) {
            array_push($months, array('month'=>$dt->format("F/Y"), 'days'=> ));
        }
        return $months;
    }

I need to get number of certain month days. How can I do that?