woocommerce_thankyou_order_id │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_thankyou_order_id', 'wp_kama_woocommerce_thankyou_order_id_filter' );

/**
 * Function for `woocommerce_thankyou_order_id` filter-hook.
 * 
 * @param  $absint 
 *
 * @return 
 */
function wp_kama_woocommerce_thankyou_order_id_filter( $absint ){

	// filter...
	return $absint;
}

$absint

-

Where the hook is called

$order_id  = apply_filters( 'woocommerce_thankyou_order_id', absint( $order_id ) );

$order_id = apply_filters( 'woocommerce_thankyou_order_id', absint( $wp->query_vars['order-received'] ) );

Where the hook is used in WooCommerce