The 'add to wishlist' button only appeared with 'buy it now' form on product page. In the products list page, the form is 'add to cart'. I think detail and list page both should add wishlist button. So i modified the code:
<?php
if (strpos($form_id, 'uc_product_add_to_cart_form_') === 0 || strpos($form_id, 'uc_catalog_buy_it_now_form_') === 0)
?>If 'add to wishlist' button is intergrated in views, it will be flexible to use.