WordPress at a glance
function is not described

WP_Widget_Recent_Posts::update() public WP 2.8.0

Handles updating the settings for the current Recent Posts widget instance.

{} It's a method of the class: WP_Widget_Recent_Posts{}

No Hooks.

Return

Array. Updated settings to save.

Usage

$WP_Widget_Recent_Posts = new WP_Widget_Recent_Posts();
$WP_Widget_Recent_Posts->update( $new_instance, $old_instance );
$new_instance(array) (required)
New settings for this instance as input by the user via WP_Widget::form().
$old_instance(array) (required)
Old settings for this instance.

Changelog

Since 2.8.0 Introduced.

Code of WP_Widget_Recent_Posts::update() WP 5.7.2

<?php
public function update( $new_instance, $old_instance ) {
	$instance              = $old_instance;
	$instance['title']     = sanitize_text_field( $new_instance['title'] );
	$instance['number']    = (int) $new_instance['number'];
	$instance['show_date'] = isset( $new_instance['show_date'] ) ? (bool) $new_instance['show_date'] : false;
	return $instance;
}