Description:
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DateTime::diff returns different results when called on both objects.

Test script:
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<?php

$date1 = new \DateTime('2015-10-25', new \DateTimeZone('UTC'));
$date2 = new \DateTime('2017-10-24', new \DateTimeZone('UTC'));

$diff1 = $date1->diff($date2);
$diff2 = $date2->diff($date1);

echo $diff1->y . ' years ' . $diff1->m . ' months ' . $diff1->d . ' days '; // outputs 1 years 11 months 29 days 
echo PHP_EOL;
echo $diff2->y . ' years ' . $diff2->m . ' months ' . $diff2->d . ' days '; // outputs 1 years 11 months 30 days 

Expected result:
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1 years 11 months 29 days 
1 years 11 months 29 days

or 

1 years 11 months 30 days 
1 years 11 months 30 days

I would expect the number of days to be identical.


Actual result:
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The number of days differs 

1 years 11 months 29 days 
1 years 11 months 30 days