public function retrieveAllPaymentmethods()
    {
        if (isset($this->_paymentMethodsArray))
            return $this;

        $obj = new stdClass();
        // Must be in specific order for checksum ---------
        $obj->MerchantID = $this->_merchantID;
        $obj->SecretCode = $this->_secretCode;
        $obj->Timestamp = $this->getTimeStamp();
        // ------------------------------------------------
        $obj->Checksum = $this->generateChecksum($obj);
        $obj->SecretCode = null;

        $this->_paymentMethods = $this->client->GetMyPaymentMethods(array('request' => $obj));

        if (isset($this->_paymentMethods->GetMyPaymentMethodsResult->PaymentMethods->PaymentMethod)) {
            $this->_paymentMethodsArray = $this->clean($this->_paymentMethods);
        }

        return $this;
    }