Wrong result from DateTimeImmutable::diff

Description

If you execute this code, it produces an extremely weird result. The first DTI is 11 minutes after what we’re ->diff() ’ing against, but when in the America/Los_Angeles TZ, it produces a very strange result. Converting the first DTI to UTC then produces the expected difference of 11 minutes.

//Difference of -1 year, 11 months, 31 days, etc.
<?php
$invalid_result = (new \DateTimeImmutable('2024-01-31 17:00:00', new \DateTimeZone('America/Los_Angeles')))
    ->diff(new \DateTimeImmutable('2024-02-01 00:49:00'));

//Difference of 11 minutes
$correct_result = (new \DateTimeImmutable('2024-01-31 17:00:00', new \DateTimeZone('America/Los_Angeles')))
    ->setTimezone(new \DateTimeZone('UTC'))
    ->diff(new \DateTimeImmutable('2024-02-01 00:49:00'));

var_dump($invalid_result);
var_dump($correct_result);

$invalid_result Resulted in this output:

object(DateInterval)#3 (10) {
  ["y"]=>
  int(-1)
  ["m"]=>
  int(11)
  ["d"]=>
  int(31)
  ["h"]=>
  int(0)
  ["i"]=>
  int(11)
  ["s"]=>
  int(0)
  ["f"]=>
  float(0)
  ["invert"]=>
  int(1)
  ["days"]=>
  int(0)
  ["from_string"]=>
  bool(false)
}

But I expected this output instead:

object(DateInterval)#2 (10) {
  ["y"]=>
  int(0)
  ["m"]=>
  int(0)
  ["d"]=>
  int(0)
  ["h"]=>
  int(0)
  ["i"]=>
  int(11)
  ["s"]=>
  int(0)
  ["f"]=>
  float(0)
  ["invert"]=>
  int(1)
  ["days"]=>
  int(0)
  ["from_string"]=>
  bool(false)
}

PHP Version

PHP 8.1

Operating System

No response

Start by reproducing the supplied PHP 8.1 script and comparing DateTimeImmutable::diff with and without setTimezone('UTC'). Trace the DateTimeImmutable::diff entry point and timezone handling, then add coverage showing that the America/Los_Angeles case produces the expected 11-minute interval.