my question is if is possible and how can i fill the description field on the payment form, whith a reference number from my slq database ?
Thank you.
You can try something like this query to define the description:
<?php $product = SELECT desc FROM table WHERE id = 'x'; ?>
And then use the $product variable to populate the value for "item_name" or whatever variable for the item description that matches the product you're using. I don't know what payment method you're using so I can't be more specific.