register_rest_field()

register_rest_field() — Registers a new field on an existing WordPress object type.

Inputs: $object_type (string|array): Object(s) the field is being registered to, “post”|”term”|”comment” etc. $attribute (string): The attribute name. $args (array): Optional. An array of arguments used to handle the registered field. Field $get_callback (callable|null): Optional. The callback function used to retrieve the field value. Default is ‘null’, the field will not be returned in the response. The function will be passed the prepared object data. Field $update_callback (callable|null): Optional. The callback function used to set and update the field value. Default is ‘null’, the value cannot be set or updated. The function will be passed the model object, like WP_Post. Field $schema (array|null): Optional. The schema for this field. Default is ‘null’, no schema entry will be returned.