1function cmx65__split_completed_order($order_id) {
 2    $order = wc_get_order($order_id);
 3 
 4    $order_product_items = array_filter(
 5        $order->get_items(),
 6        function($item){
 7            return $item instanceof WC_Order_Item_Product;
 8        }
 9    );
10 
11    if ($order_product_items <= 1) {
12        return;
13    }
14 
15    // WC_Order: https://woocommerce.github.io/code-reference/classes/WC-Order.html
16    foreach( $order_product_items as $product_item ){
17        // Create New Order For Each Product Item
18        $new_order = wc_create_order([
19            'cart_hash' => $order->get_cart_hash(),
20            'created_via' => $order->get_created_via(),
21            'customer_id' => $order->get_customer_id(),
22            'customer_note' => $order->get_customer_note(),
23            'parent' => $order->get_id(),
24            'status' => $order->get_status(),
25        ]);
26 
27        // Clone Order Information
28        $new_order->set_address($order->get_address('billing'), 'billing');
29        $new_order->set_address($order->get_address('shipping'), 'shipping');
30        $new_order->set_cart_tax($order->get_cart_tax());
31        $new_order->set_created_via($order->get_created_via());
32        $new_order->set_currency($order->get_currency());
33        $new_order->set_customer_ip_address($order->get_customer_ip_address());
34        $new_order->set_customer_user_agent($order->get_customer_user_agent());
35        $new_order->set_payment_method($order->get_payment_method());
36        $new_order->set_meta_data($order->get_meta_data());
37        $order_meta_data = $order->get_meta_data();
38        foreach($order_meta_data as $meta_data){
39            $raw_meta_data = $meta_data->get_data();
40            $new_order->add_meta_data($raw_meta_data['key'], $raw_meta_data['value']);
41        }
42        $new_order->save_meta_data();
43 
44        // Clone Product Item and Assign to New Order
45        $new_product_item = new WC_Order_Item_Product();
46        $new_product_item->set_order_id($new_order->get_id());
47        $new_product_item->set_product($product_item->get_product());
48        $new_product_item->set_subtotal($product_item->get_subtotal());
49        $new_product_item->set_total($product_item->get_total());
50        $new_product_item->save();
51        $product_meta_data = $product_item->get_meta_data();
52        foreach($product_meta_data as $meta_data){
53            $raw_meta_data = $meta_data->get_data();
54            $new_product_item->add_meta_data($raw_meta_data['key'], $raw_meta_data['value']);
55        }
56        $new_product_item->save_meta_data();
57        $new_order->add_item($new_product_item);
58 
59        // Clone Shipping Lines
60        $order_shipping_items = array_filter(
61            $order->get_items('shipping'),
62            function($item){
63                return $item instanceof WC_Order_Item_Shipping;
64            }
65        );
66        foreach( $order_shipping_items as $shipping_item ) {
67            $new_shipping_item = new WC_Order_Item_Shipping();
68            $new_shipping_item->set_order_id($new_order->get_id());
69            $new_shipping_item->save();
70 
71            $new_shipping_item->set_method_title($shipping_item->get_method_title());
72            $new_shipping_item->set_method_id($shipping_item->get_method_id());
73            $new_shipping_item->set_instance_id($shipping_item->get_instance_id());
74            $new_shipping_item->set_total($shipping_item->get_total());
75            $new_shipping_item->set_taxes($shipping_item->get_taxes());
76 
77            $shipping_meta_data = $shipping_item->get_meta_data();
78            foreach($shipping_meta_data as $meta_data){
79                $raw_meta_data = $meta_data->get_data();
80                $new_shipping_item->add_meta_data($raw_meta_data['key'], $raw_meta_data['value']);
81            }
82            $new_shipping_item->save_meta_data();
83 
84            $new_order->add_item($new_shipping_item);
85        }
86 
87        $new_order->calculate_totals();
88        $new_order->save();
89    }
90}
91 
92add_action('plugins_loaded', function(){
93    add_action('woocommerce_order_status_completed', 'cmx65_split_completed_order', 10, 1);
94});