Description:
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This change in this commit: http://git.php.net/?p=php-src.git;a=blobdiff;f=ext/date/lib/interval.c;h=dce62f3a2803db69af026105f8c862806c512bcf;hp=7fa1fc5c13f24c05ddae53b9fa952bca344ff318;hb=582f6e529e843b412d582023bf0270e47b1aa468;hpb=5d0c526199add0e4f054a57db29d882c8ad89a23 fixes so that DateTime::sub and DateTime::add handles DST transitions correctly. But derickr probably just forgot to handle forward DST transition in the DateTime::add function.

Test script:
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$tz = new DateTimeZone('Europe/London'); // A timezone that has DST

$five_hours_interval = new DateInterval('PT5H');

$date = new DateTime("2014-3-30 00:00:00", $tz);

// Add five hours and subtract 5 hours. The $newDate should then equal the date.
$five_hours_later = (clone $date)->add($five_hours_interval);
$newDate = (clone $five_hours_later)->sub($five_hours_interval);

echo $date->format('c') . "\n";
echo $newDate->format('c');



Expected result:
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2014-03-30T00:00:00+00:00
2014-03-30T00:00:00+00:00


Actual result:
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2014-03-30T00:00:00+00:00
2014-03-29T23:00:00+00:00