Virtuemart tutorial --- Add To Cart From Category

I finally figure it out.

Problem was when php want to call product ID and Name.

If you copy all code from /components/com_virtuemart/views/productdetails/tmpl/default.php, this piece of code can't call product ID or Name (<?php echo $this->product->virtuemart_product_id ?>), what you have to do is very simple, just delete "this->" so you get this: <?php echo $product->virtuemart_product_id ?>