Inconsistency with DatePeriod and `P1M` when the start date is the last day of month

[alexandre-daubois]

Description

The following code:

<?php

$period = new DatePeriod(
    new DateTimeImmutable('2025-01-31'),
    new DateInterval('P1M'),
    new DateTimeImmutable('2025-04-30'),
);

foreach ($period as $date) {
    echo $date->format('Y-m-d') . PHP_EOL;
}

Resulted in this output:

2025-01-31
2025-03-03
2025-04-03

But I expected this output instead:

2025-01-31
2025-02-28
2025-03-31

It seems PHP's having a hard time when the start month has more days than the next one.

Thanks!

PHP Version

PHP 8.3.16

Operating System

macOS 15.2

[cmb69]

Yeah, that's the usual wrap around; see e.g. https://www.php.net/manual/en/datetimeimmutable.add.php#example-2109.