WordPress at a glance
function is not described

WP_Widget_Custom_HTML::update() public WP 4.8.1

Handles updating settings for the current Custom HTML widget instance.

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

No Hooks.

Return

Array. Settings to save or bool false to cancel saving.

Usage

$WP_Widget_Custom_HTML = new WP_Widget_Custom_HTML();
$WP_Widget_Custom_HTML->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 4.8.1 Introduced.

Code of WP_Widget_Custom_HTML::update() WP 5.7.2

<?php
public function update( $new_instance, $old_instance ) {
	$instance          = array_merge( $this->default_instance, $old_instance );
	$instance['title'] = sanitize_text_field( $new_instance['title'] );
	if ( current_user_can( 'unfiltered_html' ) ) {
		$instance['content'] = $new_instance['content'];
	} else {
		$instance['content'] = wp_kses_post( $new_instance['content'] );
	}
	return $instance;
}