Allow only one product per product category in cart

Question

On this Question / Answer I have found the PHP code about how to just add one product per category in cart in Woocommerce.

The code works just fine, but I want to add the latest added product to cart and if there is already a product of that category in the cart, I want to have the oldest deleted.

add_filter( 'woocommerce_add_to_cart_validation', 'custom_checking_product_added_to_cart', 10, 3 );
function custom_checking_product_added_to_cart( $passed, $product_id, $quantity) {

// HERE Type your alert displayed message
// $message = __( 'BLA BLA YOUR MESSAGE.', 'woocommerce' );

$product_cats_object = get_the_terms( $product_id, 'product_cat' );
foreach($product_cats_object as $obj_prod_cat){
    $product_cats[] = $obj_prod_cat->slug;
}

foreach (WC()->cart->get_cart() as $cart_item ){
if( has_term( $product_cats, 'product_cat', $cart_item['product_id'] )) {
        $passed = false;
        wc_add_notice( $message, 'error' );
        break;
    }
}
return $passed;
}

It is a piece of code that comes from LoicTheAztec . It works fine but I need an extra option...

In my Woocommerce there are 5 different categories, there is just place in the cart for one item per category. The latest added item should stay, the item of the same category that is already in cart must be removed from cart. Does someone of you has a solution?

Many thanks!

Answer 1

Here is your peace of code that will remove a cart item which product category match with the current product category.

add_filter( 'woocommerce_add_to_cart_validation', 'custom_checking_product_added_to_cart', 10, 3 );
function custom_checking_product_added_to_cart( $passed, $product_id, $quantity) {

    // Getting the product categories slugs in an array for the current product
    $product_cats_object = get_the_terms( $product_id, 'product_cat' );
    foreach($product_cats_object as $obj_prod_cat)
        $product_cats[] = $obj_prod_cat->slug;

    // Iterating through each cart item
    foreach (WC()->cart->get_cart() as $cart_item_key => $cart_item ){

        // When the product category of the current product match with a cart item
        if( has_term( $product_cats, 'product_cat', $cart_item['product_id'] ))
        {
            // Removing the cart item
            WC()->cart->remove_cart_item($cart_item_key);

            // Displaying a message
            wc_add_notice( 'Only one product from a category is allowed in cart', 'notice' );

            // We stop the loop
            break;
        }
    }
    return $passed;
}

This code goes in function.php file of your active child theme (or theme) or also in any plugin file.

This code is tested and works for WooCommerce version 2.6+ and 3.0+