Wrong DateInterval when going from summer time to winter time

Description

The following code:

<?php

$timezone = new \DateTimeZone('Europe/Paris');

$periodStart = (new \DateTimeImmutable('2024-10-21'))->setTimezone($timezone)->setTime(00, 00, 00);
$periodEnd = (new \DateTimeImmutable('2024-10-27'))->setTimezone($timezone)->setTime(23, 59, 59);

var_dump($periodStart);
var_dump($periodEnd);

var_dump($timezone->getOffset($periodStart));
var_dump($timezone->getOffset($periodEnd));

var_dump($periodStart->diff($periodEnd)->format('%y years %m months %a days %H hours %I minutes %s seconds'));

Resulted in this output:

object(DateTimeImmutable)#2 (3) {
  ["date"]=>
  string(26) "2024-10-21 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
object(DateTimeImmutable)#3 (3) {
  ["date"]=>
  string(26) "2024-10-27 23:59:59.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
int(7200) // UTC+2
int(3600) // UTC+1
string(54) "0 years 0 months 6 days 23 hours 59 minutes 59 seconds"

But I expected this output instead:

object(DateTimeImmutable)#2 (3) {
  ["date"]=>
  string(26) "2024-10-21 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
object(DateTimeImmutable)#3 (3) {
  ["date"]=>
  string(26) "2024-10-27 23:59:59.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
int(7200)
int(3600)
string(54) "0 years 0 months 7 days 0 hours 59 minutes 59 seconds"

I did the same test using winter to summer time switch and the result is good.

<?php

$timezone = new \DateTimeZone('Europe/Paris');

$periodStart = (new \DateTimeImmutable('2024-03-25'))->setTimezone($timezone)->setTime(00, 00, 00);
$periodEnd = (new \DateTimeImmutable('2024-03-31'))->setTimezone($timezone)->setTime(23, 59, 59);

var_dump($periodStart);
var_dump($periodEnd);

var_dump($timezone->getOffset($periodStart));
var_dump($timezone->getOffset($periodEnd));

var_dump($periodStart->diff($periodEnd)->format('%y years %m months %a days %H hours %I minutes %s seconds'));

Output:

object(DateTimeImmutable)#2 (3) {
  ["date"]=>
  string(26) "2024-03-25 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
object(DateTimeImmutable)#3 (3) {
  ["date"]=>
  string(26) "2024-03-31 23:59:59.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(12) "Europe/Paris"
}
int(3600)
int(7200)
string(54) "0 years 0 months 6 days 22 hours 59 minutes 59 seconds"

3v4l.org links:

• Winter time to summer time: https://3v4l.org/AbF3B#v8.2.21 (good interval)
• Summer time to winter time: https://3v4l.org/5dsek#v8.2.21 (bad interval)
• Without DST transition: https://3v4l.org/eCGdj#v8.2.21 (same interval as summer to winter)

PHP Version

PHP 8.2.21 and up

Operating System

No response

Start by running the supplied DateTimeImmutable::diff reproduction for the Europe/Paris summer-to-winter transition and compare it with the winter-to-summer case. Trace the DateTimeImmutable::diff behavior and related DateTimeZone offset handling; done means the interval matches the stated expected output and the transition cases remain correct.