Description:
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property_exists from any unknown DateInterval property have a incorrect result
and throw a notice.

Test script:
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$interval = new DateInterval('P2D');
var_dump(property_exists($interval,'abcde'));

Expected result:
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bool(false)

Actual result:
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Notice:  Undefined property: DateInterval::$abcde in ... on line 3
bool(true)

Workaround
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//use get_class()
$interval = new DateInterval('P2D');
var_dump(property_exists(get_class($interval),'abcde'));