Cart work for payments and Paypal work to test

modules/cart/classes/Cartable.php

@@ -0,0 +1,19 @@
+<?php defined('SYSPATH') or die('No direct access allowed.');
+
+/**
+ * This interface ensures that all cart processing objects have the right methods
+ *
+ * @package    OSB
+ * @subpackage Cart
+ * @category   Helpers
+ * @author     Deon George
+ * @copyright  (c) 2010 Deon George
+ * @license    http://dev.leenooks.net/license.html
+ */
+interface Cartable {
+	// Render a cart line item.
+	public function cart_item();
+	// Return if this invoice is already in the cart
+	public function cart_exists();
+}
+?>