MultifieldComparer::getChangedCompatibleArray

public function getChangedCompatibleArray(Multifield\Collection $previous, Multifield\Collection $current): array
{
	$previous = clone $previous;
	$current = clone $current;

	foreach ($previous as $previousValue)
	{
		if (!$current->getById($previousValue->getId()))
		{
			// was deleted
			$previousValue->setValue('');
			$current->add($previousValue);
		}
	}

	return $current->toArray();
}