Modify “get_cart_contents_count()” to count only specific product IDs in WooCommerce cart

I have 3 ticket products in WooCommerce and want to add a name field per ticket product purchased – so if a customer buys three tickets 3 name fields are displayed to fill out in the checkout.

The code below works:

// Custom WooCommerce Checkout Fields based on Quantity
add_action( 'woocommerce_before_order_notes', 'person_details' );

function person_details($checkout) {

    global $woocommerce;

    $count = WC()->cart->get_cart_contents_count();

    $i = 1;

    for($k=2; $k<= $count; $k++) {
        $i++;

        print ('<h3>Please enter details of attendee '.$i.'</h3>');

        woocommerce_form_field( 'cstm_full_name'.$i, array(
            'type'          => 'text',
            'class'         => array('my-field-class form-row-wide'),
            'label'         => __('Full name'),
            'placeholder'   => __('Enter full name'),
            ),
        $checkout->get_value( 'cstm_full_name'.$i ));

        echo '<div class="clear"></div>';
    }
}

But this includes all products added to cart – how can I target specific Product IDs to be only be part of the cart count?

$count = WC()->cart->get_cart_contents_count();

Answer

As an alternative and most recommended way, you can use WC_Cart::get_cart_item_quantities() and in_array() in your callback function to get the cart item quantity from specific product IDs in cart

So you get:

function action_woocommerce_before_order_notes( $checkout ) {
    // True
    if ( WC()->cart ) {
        // Specific product IDs
        $product_ids = array( 30, 823, 53, 57 );

        // Initialize
        $count = 0;

        // Loop trough cart items quantities
        foreach ( WC()->cart->get_cart_item_quantities() as $product_id => $cart_item_quantity ) {
            // Checks if a value exists in an array
            if ( in_array( $product_id, $product_ids ) ) {
                $count += $cart_item_quantity;
            }
        }

        // Result
        echo '<p style="color: red; font-size: 25px;">Count = ' . $count . '</p>';
    }
}
add_action( 'woocommerce_before_order_notes', 'action_woocommerce_before_order_notes', 10, 1 );

---

OR

You could use the woocommerce_cart_contents_count filter hook, which allows you to customize the get_cart_contents_count() function to your needs:

function filter_woocommerce_cart_contents_count( $array_sum ) {
    // True
    if ( WC()->cart ) {
        // Specific product IDs
        $product_ids = array( 30, 823, 53, 57 );

        // Loop trough cart items quantities
        foreach ( WC()->cart->get_cart_item_quantities() as $product_id => $cart_item_quantity ) {
            // Checks if a value NOT exists in an array
            if ( ! in_array( $product_id, $product_ids ) ) {
                $array_sum -= $cart_item_quantity;
            }
        }
    }

    return $array_sum;
}
add_filter( 'woocommerce_cart_contents_count', 'filter_woocommerce_cart_contents_count', 10, 1 );

function action_woocommerce_before_order_notes( $checkout ) {
    // True
    if ( WC()->cart ) {
        // Get number of items in the cart.
        $count = WC()->cart->get_cart_contents_count();

        // Result
        echo '<p style="color: red; font-size: 25px;">Count = ' . $count . '</p>';
    }
}
add_action( 'woocommerce_before_order_notes', 'action_woocommerce_before_order_notes', 10, 1 );

Note: although the advantage here is that you can continue to use the get_cart_contents_count() function in this way, the disadvantage is that this function would also display the modified result when used for other purposes