WooCommerce - Automatically add bonus product - php

Question

I would like to make a script for automatically adding a bonus product to WooCommerce cart.
The bonus product would be added into the cart on adding a specific product(s). But I've never seen any improved and fully working code with features - such as automatically removing the bonus item or removing the primary product(s) from the cart.
In this solution I've come up with the below code which has the following features:
Options
Multiple required products
Automatic adding
Automatic removing (if there's no required product in the cart)
function bonus_product() {
if (is_admin()) return;
//## OPTIONS
$options = (object) array(
'bonus_product_id' => 1891, //bonus product to add
'required_products_id' => array(1873), //at least on of the specific product(s) needs to be represented in the cart
);
//function variables
$cart_items = WC()->cart->get_cart();
$bonus_product_found = false;
$required_product_found = false;
//check if the cart is not empty
if(sizeof($cart_items) > 0) {
//checking for required products. loop through the cart items
foreach ($cart_items as $key => $item) {
//bonus product already in the cart?
if($item['product_id'] == $options->bonus_product_id) {
$bonus_product_found = true;
}
//one of required products in the cart?
if(in_array($item['product_id'], $options->required_products_id)) {
$required_product_found = true;
}
}
//adding/removing bonus product
//add bonus product to the cart
if(!$bonus_product_found && $required_product_found) {
WC()->cart->add_to_cart($options->bonus_product_id);
}
//remove bonus product from the cart if none of required items is in the cart
if($bonus_product_found && !$required_product_found) {
$cart = WC()->instance()->cart;
$cart_id = $cart->generate_cart_id($options->bonus_product_id);
$cart_item_id = $cart->find_product_in_cart($cart_id);
$cart->set_quantity($cart_item_id, 0);
}
}
}
add_action( 'init', 'bonus_product' );

Answer 1

I have written an alternative version, based on Add To Cart and Remove From Cart action, which seems to be more appropriate.
$bonus_options = (object) array(
'bonus_product_id' => 1891,
'required_products_id' => array( 1873 )
);
// this function called whenever there is a product added to cart
function add_bonus_product( $cart_item_key, $product_id, $quantity, $variation_id, $variation, $cart_item_data ) {
global $bonus_options;
// is the product is eligible for bonus product?
if( in_array( $product_id, $bonus_options->required_products_id) ) {
// add the bonus product to cart
WC()->cart->add_to_cart( $bonus_options->bonus_product_id, 1, 0, array(), array( "parent_product_line_item" => $cart_item_key ) );
// later if user removes the product from cart we can use the "parent_product_line_item" to remove the bonus product as well
}
}
add_action( 'woocommerce_add_to_cart', 'add_bonus_product', 10, 6 );
// this function will be called whenever there is a product removed from cart
function remove_bonus_product( $cart_item_key, $cart ) {
$cart_items = WC()->cart->get_cart();
foreach ( $cart_items as $key => $item ) {
if( $item["parent_product_line_item"] == $cart_item_key ) {
// ok this cart item is a bonus item to the product that being removed from the cart
// So remove this too
WC()->cart->remove_cart_item( $key );
}
}
}
add_action( 'woocommerce_cart_item_removed', 'remove_bonus_product', 10, 2 );