public function getPaymentTransactionId($blOnlySessionKey = false)
    {
        $sTransactionIdKey = sprintf('pm_order_transaction_id%s', $this->getPaymentMethodName());
        $sTransactionId = (string) oxRegistry::getSession()->getVariable($sTransactionIdKey);

        return empty($blOnlySessionKey) ? $sTransactionId : $sTransactionIdKey;
    }