WooCommerce重定向到添加到购物车上的产品类别

Question

I am trying to redirect a user to previous category page when he clicks on Add to Cart on product page. But on redirect I am seeing a blank product_cat attribute. ie example.com/?product_cat= However if I echo it to woocommerce_product_thumbnail it shows the link perfectly. ie example.com/?product_cat=shoes

add_filter ('add_to_cart_redirect', 'redirect_to_previousCat');
//add_filter ('woocommerce_product_thumbnails', 'redirect_to_previousCat');
function redirect_to_previousCat() {
    global $woocommerce, $post;
    $product_cat_slug;
    $terms = get_the_terms( $post->ID, 'product_cat' );
foreach ($terms as $term) {
    $product_cat_slug = $term->slug;
    break;
}
$url=get_site_url().'?product_cat='.$product_cat_slug;
return $url;
}

Answer 1

As I mentioned in the comments, the global $post is not set up yet when the add_to_cart_action() method runs on the init hook.

Instead, I suggest you follow Wootheme's lead and get the product ID from the $_REQUEST global.

add_filter ('add_to_cart_redirect', 'redirect_to_previousCat');

function redirect_to_previousCat( $url ) {
    $product_id = absint( $_REQUEST['add-to-cart'] );
    $product_cat_slug = '';

    $terms = get_the_terms( $product_id, 'product_cat' );
    foreach ( $terms as $term ) {
        $product_cat_slug = $term->slug;
        break;
    }
    if( $product_cat_slug ){
        $url = add_query_arg( 'product_cat', $product_cat_slug, site_url() );
    }
    return $url;
}