Add a shipping to an order programmatically in Woocommerce 3
To handle this in Woocommerce 3+ use the following (from a WC_Order Order object $order):
## ------------- ADD SHIPPING PROCESS ---------------- ##// Get the customer country code$country_code = $order->get_shipping_country();// Set the array for tax calculations$calculate_tax_for = array( 'country' => $country_code, 'state' => '', // Can be set (optional) 'postcode' => '', // Can be set (optional) 'city' => '', // Can be set (optional));// Optionally, set a total shipping amount$new_ship_price = 5.10;// Get a new instance of the WC_Order_Item_Shipping Object$item = new WC_Order_Item_Shipping();$item->set_method_title( "Flat rate" );$item->set_method_id( "flat_rate:14" ); // set an existing Shipping method rate ID$item->set_total( $new_ship_price ); // (optional)$item->calculate_taxes($calculate_tax_for);$order->add_item( $item );$order->calculate_totals();$order->update_status('on-hold');// $order->save(); // If you don't update the order statusTested an works.