过滤REST API响应，只包括白名单上的一套响应对象字段。

function rest_filter_response_fields( $response, $server, $request ) {
	if ( ! isset( $request['_fields'] ) || $response->is_error() ) {
		return $response;
	}

	$data = $response->get_data();

	$fields = wp_parse_list( $request['_fields'] );

	if ( 0 === count( $fields ) ) {
		return $response;
	}

	// Trim off outside whitespace from the comma delimited list.
	$fields = array_map( 'trim', $fields );

	// Create nested array of accepted field hierarchy.
	$fields_as_keyed = array();
	foreach ( $fields as $field ) {
		$parts = explode( '.', $field );
		$ref   = &$fields_as_keyed;
		while ( count( $parts ) > 1 ) {
			$next = array_shift( $parts );
			if ( isset( $ref[ $next ] ) && true === $ref[ $next ] ) {
				// Skip any sub-properties if their parent prop is already marked for inclusion.
				break 2;
			}
			$ref[ $next ] = isset( $ref[ $next ] ) ? $ref[ $next ] : array();
			$ref          = &$ref[ $next ];
		}
		$last         = array_shift( $parts );
		$ref[ $last ] = true;
	}

	if ( wp_is_numeric_array( $data ) ) {
		$new_data = array();
		foreach ( $data as $item ) {
			$new_data[] = _rest_array_intersect_key_recursive( $item, $fields_as_keyed );
		}
	} else {
		$new_data = _rest_array_intersect_key_recursive( $data, $fields_as_keyed );
	}

	$response->set_data( $new_data );

	return $response;
}