WP_REST_Controller::add_additional_fields_to_object( array $response_data, WP_REST_Request $request ): array

419	protected function add_additional_fields_to_object( $response_data, $request ) {420 421		$additional_fields = $this->get_additional_fields();422 423		$requested_fields = $this->get_fields_for_response( $request );424 425		foreach ( $additional_fields as $field_name => $field_options ) {426			if ( ! $field_options['get_callback'] ) {427				continue;428			}429 430			if ( ! rest_is_field_included( $field_name, $requested_fields ) ) {431				continue;432			}433 434			$response_data[ $field_name ] = call_user_func(435				$field_options['get_callback'],436				$response_data,437				$field_name,438				$request,439				$this->get_object_type()440			);441		}442 443		return $response_data;444	}