function nextDay($date,$month){
//1获取今天的时间 $date 时间 $date_day 今天的日期
$date_day =date('d', strtotime($date));
//2获取N月后的时间
$lastday = strtotime("$date +$month months");
$last_day =date('d',$lastday);
$day_benlastday = date('Y-m-d', $lastday);
$day_t=date('Y-m-t',strtotime("$day_benlastday -1 month"));
$day_benlast_day= date('t',strtotime($day_t));
//获取当天日期
$Same_day = date('d', strtotime($date));
//判断N月后的天数是否比当前时间小
if($day_benlastday<$Same_day &&$last_day!==$date_day){
$day = $day_benlast_day;
$day = date('Y',$lastday).'-'.date('m',strtotime($day_t)).'-'.$day.' 23:59:59';
}else{
$day = $Same_day;
$day = date('Y',$lastday).'-'.date('m',$lastday).'-'.$day.' 23:59:59';
}
return $day;
}
echo nextDay('2020-01-30 05:05:05',1);