Save The Eway Transaction ID As Post Meta

/* Line 417 - gateway-eway.php */
case 'true':

                        //Save The Eway Transaction ID
                        if ( ! empty( $parsed_response['EWAYTRXNNUMBER'] ) )
                        update_post_meta( $order_id, 'Eway Transaction ID',  $parsed_response['EWAYTRXNNUMBER'] );

                        // Add order note
                        $order->add_order_note(sprintf(__('eWAY payment completed', 'woothemes')));

                        // Payment complete
                        $order->payment_complete();

                        // Remove cart
                        $woocommerce->cart->empty_cart();

                        // Empty awaiting payment session
                        unset($_SESSION['order_awaiting_payment']);

                        // Return thank you page redirect
                        return array(
                            'result' => 'success',
                            'redirect' => add_query_arg('key', $order->order_key, add_query_arg('order', $order_id, get_permalink(get_option('woocommerce_thanks_page_id'))))
                        );

                        break;