I'm not quite sure what you are trying to achieve.
Looking at the SELECT statement, you are filtering by product category, so I assume you want to show all items within that category when the menu link is clicked.
Assuming your recordset returns all items without any parameters, then you need only to filter by product category.
the link in this case would be something like...
<a href="products.php?id_category_product=1"></a> where the number in red is the product id url parameter value