Great contribution, but I am noticing that it doesn't work out as well as it is intended too. When you go to the main product that has "recommended products" you can either buy the main product which takes you to a different page and you no longer see the "recommended products". Or if you click on any one of the "recommended products" you are taken to their product info page, but youy have not added the main product to your basket yet. So waht is happening is you are really not upselling or cross selling, it is just showing other products.
I would think that the "recommended products" should show up in the shopping_cart.php page instead of the product_info.php page. Say you add a product to your cart, then go to the cart and it would show the "recommended products" there. Then you already have the main product ready for purchase, and now moving to the "recommended products" product info page would allow you to add them as well. Just seems more logical and would flow better.
If anyone has some thoughts on how to implement this into the shopping_cart.php page, please do so. Thanks.