WP_REST_Controller::update_additional_fields_for_object PHP Method

    protected function update_additional_fields_for_object($object, $request)
    {
        $additional_fields = $this->get_additional_fields();
        foreach ($additional_fields as $field_name => $field_options) {
            if (!$field_options['update_callback']) {
                continue;
            }
            // Don't run the update callbacks if the data wasn't passed in the request.
            if (!isset($request[$field_name])) {
                continue;
            }
            call_user_func($field_options['update_callback'], $request[$field_name], $object, $field_name, $request, $this->get_object_type());
        }
    }