How to automatically set cross-sells in WooCommerce based on product category

Question

I'm trying to edit the cross-sell section of the cart page in WooCommerce. I want to display random products from the same category in the cross-sell section.

For example, someone adds something from the category women's fashion then it will display other products in the cross-sell section from the same category.

or if they have items from multiple categories to then just pick two at random.

Is there a way of doing this or is it a case of having to go through every product individually to select the cross-sell products?

Answer 1

Following code returns automatically $cross_sells IDs that belong to the product categor(y)(ies) from the products in the cart.

function filter_woocommerce_cart_crosssell_ids( $cross_sells, $cart ) {
    // Initialize
    $product_cats_ids = array();
    $product_cats_ids_unique = array();

    foreach ( $cart->get_cart() as $cart_item ) {       
        // Get product id
        $product_id = $cart_item['product_id'];

        // Get current product categories id(s) & add to array
        $product_cats_ids = array_merge( $product_cats_ids, wc_get_product_term_ids( $product_id, 'product_cat' ) );
    }

    // Not empty
    if ( !empty( $product_cats_ids ) ) {
        // Removes duplicate values
        $product_cats_ids_unique = array_unique( $product_cats_ids, SORT_REGULAR );

        // Get product id(s) from a certain category, by category-id
        $product_ids_from_cats_ids = get_posts( array(
            'post_type'   => 'product',
            'numberposts' => -1,
            'post_status' => 'publish',
            'fields'      => 'ids',
            'tax_query'   => array(
                array(
                    'taxonomy' => 'product_cat',
                    'field'    => 'id',
                    'terms'    => $product_cats_ids_unique,
                    'operator' => 'IN',
                )
            ),
        ) );

        // Removes duplicate values
        $cross_sells = array_unique( $product_ids_from_cats_ids, SORT_REGULAR );
    }

    return $cross_sells;
}
add_filter( 'woocommerce_cart_crosssell_ids', 'filter_woocommerce_cart_crosssell_ids', 10, 2 );

Note: 'numberposts' => -1 means ALL, this can be adapted to your needs

---

The limit ('posts_per_page') can be set via the woocommerce_cross_sells_total filter hook

function filter_woocommerce_cross_sells_total( $limit ) {
    // Set limit
    $limit = 4;
    
    return $limit;
}
add_filter( 'woocommerce_cross_sells_total', 'filter_woocommerce_cross_sells_total', 10, 1 );