php获取指定月的某一天的日期

   /**

      * 获取指定月的第几天的日期

      * @$year 年，$month月，$day天，$format显示时间的格式,$last是否该月最后一天

      * @return $str

      */

function getMonthDay($year,$month,$day,$format='Y-m-d',$last=0){

        if($last){

            $time=new DateTime($day);        

            $d=strtotime($time->format("Y-m-d"));

            $d=date("t",$d);

            $time->setDate($year,$month,$d);

        }else{

            $time=new DateTime();

            $time->setDate($year,$month,$day);

        }

        return $time->format($format);

    }