如何正确初始化Woocommerce购物车

I have a custom template file, rendering some products and their Add To Cart buttons, that I am trying to implement manually. When Add to Cart is pressed, the page is reloaded and a $_POST variable containing some data adds the new products. 'cart_contents_count' also reflects the added item. However, when I go to the cart page, it's empty. Please see the following code.I have a custom template file, rendering some p