InvoiceExist::save

public function save()
{
	$result = new Main\Result();
	if (!$this->isChanged())
	{
		return $result;
	}

	$changedFields = array_keys($this->previousRecurringFields);
	$updateFields = array_intersect_key($this->recurringFields, array_flip($changedFields));
	$r = $this->update($updateFields);
	if (!$r->isSuccess())
	{
		return $r;
	}

	$this->onAfterSave($updateFields);
	$this->previousRecurringFields = [];

	return $result;
}