public function save( $post_id ) {

		if ( ! llms_verify_nonce( 'lifterlms_meta_nonce', 'lifterlms_save_data' ) ) {
			return -1;
		}

		$order = llms_get_post( $post_id );
		if ( ! $order || ! is_a( $order, 'LLMS_Order' ) ) {
			return 0;
		}

		$fields = array(
			'payment_gateway',
			'gateway_customer_id',
			'gateway_subscription_id',
			'gateway_source_id',
		);

		foreach ( $fields as $key ) {

			if ( isset( $_POST[ $key ] ) ) {
				$order->set( $key, llms_filter_input_sanitize_string( INPUT_POST, $key ) );
			}
		}

		$this->save_remaining_payments( $order );

		return 1;

	}