public function createLog($password_id, $nbr, $created_at = null)
{
$log = new LoyaltyCard_Model_Customer_Log();
$log->setCardId($this->getCardId())->setCustomerId($this->getCustomerId())->setPasswordId($password_id)->setNumberOfPoints($nbr);
if ($created_at) {
$log->setCreatedAt($created_at);
}
$log->save();
return $this;
}