/**
		 * Fired when a LifterLMS order or transaction changes status.
		 *
		 * The first dynamic portion of this hook, `$post_type`, refers to the unprefixed object post type ('order|transaction').
		 * The second dynamic portion of this hook, `$new_status`, refers to the new object status.
		 *
		 * @since Unknown
		 *
		 * @param LLMS_Order|LLMS_Transaction $object     The LifterLMS order or transaction instance.
		 * @param string                      $old_status The previous order or transaction status.
		 * @param string                      $new_status The new order or transaction status.
		 */
		do_action( "lifterlms_{$post_type}_status_{$new_status}", $obj, $old_status, $new_status );

	}

	/**
	 * Validate a gateway can be used to process the current action / transaction.
	 *
	 * @since 3.10.0
	 *
	 * @param string           $gateway_id Gateway's id.
	 * @param LLMS_Access_Plan $plan       Instance of the LLMS_Access_Plan related to the action/transaction.
	 * @return WP_Error|LLMS_Payment_Gateway WP_Error or LLMS_Payment_Gateway subclass.
	 */
	private function validate_selected_gateway( $gateway_id, $plan ) {

		$gateway = llms()->payment_gateways()->get_gateway_by_id( $gateway_id );
		$err     = new WP_Error();

		// Valid gateway.
		if ( is_subclass_of( $gateway, 'LLMS_Payment_Gateway' ) ) {