Title: WP_REST_Controller::add_additional_fields_to_object
Published: December 6, 2016
Last modified: May 20, 2026

---

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

## In this article

 * [Parameters](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#parameters)
 * [Return](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#return)
 * [Source](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#source)
 * [Related](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#related)
 * [Changelog](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#wp--skip-link--target)

Adds the values from additional fields to a data object.

## 󠀁[Parameters](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#parameters)󠁿

 `$response_data`arrayrequired

Prepared response array.

`$request`[WP_REST_Request](https://developer.wordpress.org/reference/classes/wp_rest_request/)
required

Full details about the request.

## 󠀁[Return](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#return)󠁿

 array Modified data object with additional fields.

## 󠀁[Source](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#source)󠁿

    ```php
    protected function add_additional_fields_to_object( $response_data, $request ) {

    	$additional_fields = $this->get_additional_fields();

    	$requested_fields = $this->get_fields_for_response( $request );

    	foreach ( $additional_fields as $field_name => $field_options ) {
    		if ( ! $field_options['get_callback'] ) {
    			continue;
    		}

    		if ( ! rest_is_field_included( $field_name, $requested_fields ) ) {
    			continue;
    		}

    		$response_data[ $field_name ] = call_user_func(
    			$field_options['get_callback'],
    			$response_data,
    			$field_name,
    			$request,
    			$this->get_object_type()
    		);
    	}

    	return $response_data;
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/rest-api/endpoints/class-wp-rest-controller.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/7.0/src/wp-includes/rest-api/endpoints/class-wp-rest-controller.php#L419)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/rest-api/endpoints/class-wp-rest-controller.php#L419-L444)

## 󠀁[Related](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#related)󠁿

| Uses | Description | 
| [rest_is_field_included()](https://developer.wordpress.org/reference/functions/rest_is_field_included/)`wp-includes/rest-api.php` |

Given an array of fields to include in a response, some of which may be `nested.fields`, determine whether the provided field should be included in the response body.

  | 
| [WP_REST_Controller::get_fields_for_response()](https://developer.wordpress.org/reference/classes/wp_rest_controller/get_fields_for_response/)`wp-includes/rest-api/endpoints/class-wp-rest-controller.php` |

Gets an array of fields to be included on the response.

  | 
| [WP_REST_Controller::get_object_type()](https://developer.wordpress.org/reference/classes/wp_rest_controller/get_object_type/)`wp-includes/rest-api/endpoints/class-wp-rest-controller.php` |

Retrieves the object type this controller is responsible for managing.

  | 
| [WP_REST_Controller::get_additional_fields()](https://developer.wordpress.org/reference/classes/wp_rest_controller/get_additional_fields/)`wp-includes/rest-api/endpoints/class-wp-rest-controller.php` |

Retrieves all of the registered additional fields for a given object-type.

  |

## 󠀁[Changelog](https://developer.wordpress.org/reference/classes/wp_rest_controller/add_additional_fields_to_object/?output_format=md#changelog)󠁿

| Version | Description | 
| [4.7.0](https://developer.wordpress.org/reference/since/4.7.0/) | Introduced. |

## User Contributed Notes

You must [log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fdeveloper.wordpress.org%2Freference%2Fclasses%2Fwp_rest_controller%2Fadd_additional_fields_to_object%2F)
before being able to contribute a note or feedback.