PHP - How to calculate one month or one year later

Question

I'd like to calculate next billing date of Recurly plan in PHP. There are 2 types of billing cycle: yearly | monthly. I tried to use DateTime and DateInterval classes, but didn't get expected results.

<?php
$referenceTime = new \DateTime('2016-01-31');
$oneMonthLater = $referenceTime->modify('+1 month');
var_dump($oneMonthLater);
// public 'date' => string '2016-03-02 00:00:00.000000'

Adding one month to the 31st of Januray gives me the second of March and not the 29th (or 28th) of February as I would expect.

The same for the 31st of August:

<?php
$referenceTime = new \DateTime('2016-08-31');
$oneMonthLater = $referenceTime->modify('+1 month');
var_dump($oneMonthLater);
// public 'date' => string '2016-10-01 00:00:00.000000'

If yearly, I expect Feb 29, 2016 + 1 year => Feb 28, 2017

Thanks.

Show us what you have done so far... It will be easier for us to answer. — d.coder, Dec 06 '16 at 11:40
$next_bill_date = new DateTime(); if ($plan_interval_unit == 'year') { $interval_spec = 'P'.$plan['plan_interval_length'].'Y'; } else if ($plan_interval_unit == 'month') { $interval_spec = 'P'.$plan['plan_interval_length'].'M'; } $next_bill_date->add(new DateInterval($interval_spec)); — Paul Z., Dec 06 '16 at 11:41
Add it in your question please. Hard to read/understand here... :( — d.coder, Dec 06 '16 at 11:42

score 3 · Answer 1 · answered Dec 06 '16 at 11:51

Try this, if date > 28 use last day of next month else use +1 month

$get_date = strtotime("31-01-2016");
$dt = explode("-",$get_date);
$dt = $dt[0];
var_dump(($dt > 28) ? date("d-m-Y", strtotime("31-01-2016 last day of next month")) : date("d-m-Y", strtotime("31-01-2016 +1 month")));

DEMO

score 1 · Answer 2 · answered Dec 06 '16 at 11:48

You can call modify with PHP's DateTime object to calculate the next date relative to the current date. The following code shows how you would do it with your specific situation.

$next_bill_date = new DateTime();
switch($plan_interval_unit) {
    case "year":
        $next_bill_date->modify("last day of next month");
        break;

    case "month":
        $next_bill_date->modify("last day of this month next year");
        break;
}

score 0 · Answer 3 · answered Dec 06 '16 at 11:44

May be something like that:

if (date('d') !== date('d', strtotime('+1 month'))
    date ('Y-m-d H:i:s', strtotime('last day of next month'));

if (date('d') !== date('d', strtotime('+1 year'))
    date ('Y-m-d H:i:s', strtotime('last day of this month next year'));

score 0 · Answer 4 · answered Dec 06 '16 at 12:18

0

You can use PHP inbuilt strtotime() function

// One month from today
$date = date('Y-m-d', strtotime('+1 month'));

// One month from a specific date
$date = date('Y-m-d', strtotime('+1 month', strtotime('2016-12-06')));

answered Dec 06 '16 at 12:18

Hiren Makwana

1,976
2
13
28

This doesn't solve the problem specified though unless I'm missing something? If I use the date `2016-01-31` the result is actually `Wed, 02 Mar 2016...` but the OP was looking for it to return _"29th (or 28th) of February_". – Henders Dec 06 '16 at 12:25
You need past month OR future month ?! – Hiren Makwana Dec 06 '16 at 12:27
I answered myself. Thank you for your help! – Paul Z. Dec 06 '16 at 12:51

score 0 · Accepted Answer · answered Dec 06 '16 at 12:42

function get_next_billing_date($now, $type, $format = 'Y-m-d')
{
    $date = new DateTime($now);

    $y = $date->format("Y");
    $m = $date->format("m");
    $d = $date->format("d");

    if ($type == 'year') {
        $y++;
        if ($m == 2 && $d == 29) {
            $d = 28;
        }
    } else if ($type == 'month') {
        if ($m == 12) {
            $y++;
            $m = 1;
        } else {
            $m++;
        }

        $first_date = sprintf("%04d-%02d-01", $y, $m);
        $last_day_of_next_month = date('t', strtotime($first_date));

        if ($d > $last_day_of_next_month) {
            $d = $last_day_of_next_month;
        }
    } else {
        // not supported
        return false;
    }

    $date->setDate($y, $m, $d);

    return $date->format($format);
}

PHP - How to calculate one month or one year later

5 Answers5