added unittests for bug #68549

[ComaVN]

https://bugs.php.net/bug.php?id=68549

Setting a DateTime's unix timestamp to a moment during around the transition from DST back to standard time fails in some cases.

Likewise, setting the timezone of a DateTime object representing such a moment to a DST-supporting timezone fails.

The setTimezone bug appears to have already been fixed for PHP 8.1, but not in 7.4

The setTimestamp bug appears in all versions I tested (7.1 and up)

[ComaVN]

I actually fixed it I think, I'll make a new PR for that

[heiglandreas]

I would rather get to the point where we can call this:

$tz = new DateTimeZone($timezone);
$dt = new DateTimeImmutable('@' . $timestamp, $tz);
printf("%s %d -> %d %s\n", $timezone, $timestamp, $dt->getTimestamp(), $dt->format(DateTimeInterface::ISO8601));

which would internally create the DateTimeImmutable-Object with the timestamp and set the timezone afterwards.

But more interesting would be something like the following:

$tz = new DateTimeZone('Europe/Amsterdam');
$dt = new DateTimeImmutable('2021-10-31T02:30:00+02:00', $tz);
echo $dt->format(DateTimeInterface::ISO8601);
// Sun Oct 31 02:30:00 CEST 2021
echo $dt->getTimezone()->getName();
// Europe/Amsterdam
$dt = new DateTimeImmutable('2021-10-31T02:30:00+01:00', $tz);
echo $dt->format(DateTimeInterface::ISO8601);
// Sun Oct 31 02:30:00 CET 2021
echo $dt->getTimezone()->getName();
// Europe/Amsterdam

Which would require a BC-break as it suddenly uses the second parameter in the constructor that previously was ignored when a Timezoneinformation was given in the timestring (and a timestamp implicitly has a timezone information)