WordPress at a glance
function is not described

wc_get_order_id_by_order_key() WC 1.0

Finds an Order ID based on an order key.

No Hooks.

Return

Int. The ID of an order, or 0 if the order could not be found.

Usage

wc_get_order_id_by_order_key( $order_key );
$order_key(string) (required)
An order key has generated by.

Code of wc_get_order_id_by_order_key() WC 5.2.2

<?php
function wc_get_order_id_by_order_key( $order_key ) {
	$data_store = WC_Data_Store::load( 'order' );
	return $data_store->get_order_id_by_order_key( $order_key );
}