phpwordpresswoocommerceproductcart

Force specific WooCommerce product to be sold in separate order

I'm trying to force a specific product in WooCommerce to be sold separately. I however want this product to sell in unlimited quantity.

Based on Force sold individually product to be bought alone in WooCommerce answer code which works quite well, I am currently using:

function filter_woocommerce_add_to_cart_validation( $passed, $product_id, $quantity, $variation_id = null, $variations = null ) {
    // Product id to bought alone 
    $product_id_alone = 666;
 
    // Set variable
    $alone = true;
 
    // If passed
    if ( $passed ) {
        // If cart is NOT empty when a product is added
        if ( !WC()->cart->is_empty() ) {
 
            // If product id added = product id alone
            if ( $product_id_alone == $product_id ) {
                $alone = false;
            } else {
                // Generate a unique ID for the cart item
                $product_cart_id = WC()->cart->generate_cart_id( $product_id_alone );
 
                // Check if product is in the cart
                $in_cart = WC()->cart->find_product_in_cart( $product_cart_id );
 
                // If product is already in cart
                if ( $in_cart ) {
                    $alone = false;
                }
            }
        } else {
 
            if ( $product_id_alone == $product_id) {
                $alone = true;         
            }
        }
    }
 
    if ( $alone == false ) {
        // Set error message
        $message = 'Product 666 must be bought separately.';
        wc_add_notice( __( $message, 'woocommerce' ), 'error' );
        $passed = false;
    }
 
    return $passed;
}
add_filter( 'woocommerce_add_to_cart_validation', 'filter_woocommerce_add_to_cart_validation', 10, 5 );

If the cart is empty, I can add product with ID 666 with a custom quantity.

Once product ID 666 has been added to the cart, I can't add another product to the cart.

And if I start by adding another product to an empty cart, I can't add product ID 666 to the cart.

The issue is that if I add product ID 666 to an empty cart I can't increase quantity of product 666 by adding more of that product into the cart.

Solution

  • To force a specific product to be sold alone, in a separate order, use:

    function filter_woocommerce_add_to_cart_validation( $passed, $product_id, $quantity, $variation_id = null, $variations = null ) {
    // Product id to bought alone 
    $product_id_alone = 666;

    // Set variable
    $flag = false;

    // If cart is NOT empty when a product is added
    if ( ! WC()->cart->is_empty() ) {
        // Generate a unique ID for the cart item
        $product_cart_id = WC()->cart->generate_cart_id( $product_id_alone );

        // Check if product is in the cart
        $in_cart = WC()->cart->find_product_in_cart( $product_cart_id );

        // If product is already in cart & product ID added is not equal to product ID alone
        if ( $in_cart && ( $product_id != $product_id_alone ) ) {
            $flag = true;
        // Product ID alone is NOT in cart & product ID added is equal to product ID alone
        } elseif( ! $in_cart && ( $product_id == $product_id_alone ) ) {
            $flag = true;
        }
    }

    // True
    if ( $flag ) {
        // Set error message
        wc_add_notice( sprintf(
            __( 'Product %s must be bought separately', 'woocommerce' ),
            $product_id_alone,
        ), 'error' );

        // Passed = false
        $passed = false;
    }

    return $passed;
}
add_filter( 'woocommerce_add_to_cart_validation', 'filter_woocommerce_add_to_cart_validation', 10, 5 );

    When adding the product with ID 666:

    When a product with a different ID is added: