WooCommerce: Custom Order Number Based On Billing Customers Initials And Random Number between 10,000 and 99,999

woocommerce-custom-order-number-based-on-billing-initials-and-random-number.php

/**
 * Generate an order ID based on the billing customers initials and a random number between 10000 and 99999
 *
 * @author Wil Brown zeropointdevelopment.com
 * @param $order_id
 *
 * @return string
 * @throws Exception
 */
function zpd_change_woocommerce_order_number( $order_id ) {
	$order = new WC_Order($order_id);

	$billing_first_name = strtoupper( $order->get_billing_first_name() );
	$billing_last_name = strtoupper( $order->get_billing_last_name() );
	$random_order_number = random_int(10000, 99999);

	return $billing_first_name[0] . $billing_last_name[0] . '-' . $random_order_number;
}
add_filter('woocommerce_order_number', 'zpd_change_woocommerce_order_number');

Hi. Great code there! Is it possible to apply this only on new orders but not existing orders?

This will only apply to new orders after you have copied the code into your child theme's functions.php file so it won't touch existing orders.