Save the sum of all specific order item custom fields as order meta data in WooCommerce
问题 Following my previous question " Save WooCommerce order item custom fields sum as a new meta data" , when an order is placed, some order item custom meta data quantity , assemblycost and calculated_field (which value is to quantity x assemblycost ) are saved. How can I save as custom order meta data the sum of all order items calculated_field values? For example, a sample order would look like so: Product A: assemblycost: 10 quantity: 2 calculated_field: 20 Product B: assemblycost: 15