WordPress at a glance
function is not described

_register_widget_update_callback() WP 2.8.0

Registers the update callback for a widget.

No Hooks.

Return

Null. Nothing.

Usage

_register_widget_update_callback( $id_base, $update_callback, $options, ...$params );
$id_base(string) (required)
The base ID of a widget created by extending WP_Widget.
$update_callback(callable) (required)
Update callback method for the widget.
$options(array)
Widget control options. See wp_register_widget_control().
Default: empty array
...$params(mixed) (required)
Optional additional parameters to pass to the callback function when it's called.

Notes

  • Global. Array. $wp_registered_widget_updates

Changelog

Since 2.8.0 Introduced.
Since 5.3.0 Formalized the existing and already documented ...$params parameter by adding it to the function signature.

Code of _register_widget_update_callback() WP 5.5.2

<?php
function _register_widget_update_callback( $id_base, $update_callback, $options = array(), ...$params ) {
	global $wp_registered_widget_updates;

	if ( isset( $wp_registered_widget_updates[ $id_base ] ) ) {
		if ( empty( $update_callback ) ) {
			unset( $wp_registered_widget_updates[ $id_base ] );
		}
		return;
	}

	$widget = array(
		'callback' => $update_callback,
		'params'   => $params,
	);

	$widget                                   = array_merge( $widget, $options );
	$wp_registered_widget_updates[ $id_base ] = $widget;
}