CI-Merchant with Sagepay - codeigniter-2

Question

Has anyone had any luck using SagePay Direct with CI-Merchant? So far the only response I am getting is:
Merchant_response Object
(
[_status:protected] => failed
[_message:protected] =>
[_reference:protected] =>
[_data:protected] =>
[_redirect_url:protected] =>
[_redirect_method:protected] => GET
[_redirect_message:protected] =>
[_redirect_data:protected] =>
)
I haven't used SagePay before and need to get this working urgently. I have added my IP address to the SagePay testing area but am not testing on https as am just on my localhost at the moment.
My code looks like:
public function process_payment()
{
$settings = array (
'vendor' => 'XXX',
'test_mode' => TRUE,
'simulator_mode' => FALSE,
);
$this->merchant->initialize($settings);
//get customer details
$this->load->library('custom_cart');
$customer = $this->custom_cart->get_customer_invoice_info();
$customer_name = '';
if ( ! empty($customer['title'])) $customer_name .= $customer['title'] .' ';
$customer_name .= $customer['forename'];
$customer_name .= $customer['surname'];
$customer_street = $customer['address1'];
$customer_street2 = $customer['address2'];
if ( ! empty($customer['address3'])) $customer_street2 .= $customer['address3'];
//order details
$amt = $this->custom_cart->order_total();
$get_curr = $this->custom_cart->get_currency();
$currencycode = $get_curr['name'];
$shippingamt = $this->custom_cart->shipping_cost();
$itemamt = $this->custom_cart->order_subtotal();
$taxamt = '0';
$invnum = $this->custom_cart->customer_order_no();
$params = array(
'description'=> 'Online order',
'currency'=> $currencycode,
'transaction_id'=> $invnum,
'email'=> $customer['email_address'],
'first_name'=> $customer['forename'],
'last_name'=> $customer['surname'],
'address1'=> $customer_street,
'address2'=> $customer_street2,
'city'=> $customer['town_city'],
'postcode'=> $customer['postcode'],
'country'=> $customer['country'],
'region'=> $customer['county'],
'phone'=> $customer['phone'],
'Amount'=> $amt,
'card_no'=> $this->input->post('creditcard'),
'name'=> $customer_name,
'card_type' => $this->input->post('creditcardtype'),
'exp_month'=> $this->input->post('cardmonth'),
'exp_year' => $this->input->post('cardyear'),
'csc'=> $this->input->post('cardsecurecode')
);
$response = $this->merchant->purchase($params);
echo '<pre>';
print_r($response);
}
(all the values for the params are valid and I have checked the correct values are passed to them. Vendor name is masked here)

Answer 1

Finally tracked down the problem - I was passing through two digits for the year and this is where it was failing (I forgot on my previous merchant I was adding in the 20 prefix)! Thank you for your help. (If anyone has a similar problem I tracked it down by echoing a response from each function in the function trail)