Convert date to current month date

Question

I need to convert any date to a date within 1 month from today. Dates that are smaller than today should be converted to next month.

For example, current day is 2018-09-11 and dates are:

$dates = ['2018-08-01', '2018-09-11', '2018-09-15', '2018-10-15', '2018-12-31', '2019-01-01', '2019-01-31'];

Results should be as follows, respectively:

$result = ['2018-10-01', '2018-09-11', '2018-09-15', '2018-09-15', '2018-09-30', '2018-10-01, '2018-09-30'];

Edit: I have tried so far using strtotime('+1 month') but it fails on dates such as 2018-10-31 since it'll give 2018-12-01. It also fails on using strtotime('-1 month') on dates such as 2018-10-31 where it gives 2018-10-01 instead of 2018-09-30.

My current solution is following, but I believe it can be done MUCH simpler somehow:

$timestamp = strtotime('2018-10-31');
if (date('d', $timestamp) > date('t')) {
    $date = date('Y-m-t');
} elseif(date('d', $timestamp) < date('d')) {
    $year = date('Y');
    $month = date('m') == 12 ? 1 : (intval(date('n')) + 1);
    if ($month < 10) {
        $month = '0'.$month;
    }
    $day = date('d', $timestamp);
    $date = $year . '-' . $month . '-' . $day;
} else {
    $date = date('Y-m') . '-' . date('d', $timestamp);
}

Answer 1

You can use

if('2018-09-11'<date("Y-m-d"))
date("Y-m-d", strtotime("+1 month", '2018-09-11'));

for example