[php-src] Issue #10583: Regression in DateTime[Immutable]->modify with invalid unit since 8.1.15 and 8.2.2

Issue: https://github.com/php/php-src/issues/10583 Author: marc-mabe ### Description The following code: https://3v4l.org/EMU1K ```php <?php $dt = new DateTime('2015-01-01 00:00:00+00:00'); var_dump($dt->format('c')); var_dump($dt->modify('+1 s')->format('c')); $dt = new DateTimeImmutable('2015-01-01 00:00:00+00:00'); var_dump($dt->format('c')); var_dump($dt->modify('+1 s')->format('c')); ``` Resulted in this output: ``` string(25) "2015-01-01T00:00:00+00:00" string(25) "2015-01-01T00:00:00+01:00" string(25) "2015-01-01T00:00:00+00:00" string(25) "2015-01-01T00:00:00+01:00" ``` But I expected this output instead: ``` string(25) "2015-01-01T00:00:00+00:00" string(25) "2015-01-01T00:00:00+00:00" string(25) "2015-01-01T00:00:00+00:00" string(25) "2015-01-01T00:00:00+00:00" ``` As you can see it's modifying the time zone offset from +00:00 to +01:00 instead of doing nothing as s is not a valid unit according to https://www.php.net/manual/en/datetime.formats.relative.php. It's interesting here because s is a common mistake as abbr. of second & sec where also ms and µs would be valid (which is another topic) but there is also no documented way of modifying the time zone using modify and in this particular case it's effectively moving backward instead of forward. ### PHP Version PHP 8.1.15 / PHP 8.2.2 ### Operating System Linux