Hi!
The main process is as follows:
1) Create an empty module as described here:
http://kb.x-cart.com/display/XDD/How+to+create+a+module
2) Create the file Model/Product.php script inside your module with the following content:
PHP Code:
<?php
namespace <YOUR-NAME-SPACE>;
class Product extends \XLite\Model\Product implements \XLite\Base\IDecorator
{
/**
* @Column(type="integer")
*/
protected $my_int_property;
/**
* @Column(type="string", length="32")
*/
protected $my_string_propery;
}
You should use your own namespace in the script, of course. Within the example, I created two properties: integer property and string one.
Once you rebuild cache X-Cart 5 will update tables and new field will appear in the database.
If you can give more details about how you want to display on invoice, I can help you with this part as well.
Tony.