WordPress at a glance
function is not described

Automattic\WooCommerce\Admin\API\Reports

Controller::get_order_number() public WC 1.0

Get the order number for an order. If no filter is present for woocommerce_order_number, we can just return the ID. Returns the parent order number if the order is actually a refund.

{} It's a method of the class: Controller{}

No Hooks.

Return

String. Nothing.

Usage

$Controller = new Controller();
$Controller->get_order_number( $order_id );
$order_id(int) (required)
Order ID.

Code of Controller::get_order_number() WC 5.2.2

<?php
public function get_order_number( $order_id ) {
	$order = wc_get_order( $order_id );

	if ( ! $order instanceof \WC_Order ) {
		return null;
	}

	if ( 'shop_order_refund' === $order->get_type() ) {
		$order = wc_get_order( $order->get_parent_id() );
	}

	if ( ! has_filter( 'woocommerce_order_number' ) ) {
		return $order->get_id();
	}

	return $order->get_order_number();
}