WP_Widget::update_callback( int $deprecated = 1 )

	public function update_callback( $deprecated = 1 ) {
		global $wp_registered_widgets;

		$all_instances = $this->get_settings();

		// We need to update the data
		if ( $this->updated )
			return;

		if ( isset($_POST['delete_widget']) && $_POST['delete_widget'] ) {
			// Delete the settings for this instance of the widget
			if ( isset($_POST['the-widget-id']) )
				$del_id = $_POST['the-widget-id'];
			else
				return;

			if ( isset($wp_registered_widgets[$del_id]['params'][0]['number']) ) {
				$number = $wp_registered_widgets[$del_id]['params'][0]['number'];

				if ( $this->id_base . '-' . $number == $del_id )
					unset($all_instances[$number]);
			}
		} else {
			if ( isset($_POST['widget-' . $this->id_base]) && is_array($_POST['widget-' . $this->id_base]) ) {
				$settings = $_POST['widget-' . $this->id_base];
			} elseif ( isset($_POST['id_base']) && $_POST['id_base'] == $this->id_base ) {
				$num = $_POST['multi_number'] ? (int) $_POST['multi_number'] : (int) $_POST['widget_number'];
				$settings = array( $num => array() );
			} else {
				return;
			}

			foreach ( $settings as $number => $new_instance ) {
				$new_instance = stripslashes_deep($new_instance);
				$this->_set($number);

				$old_instance = isset($all_instances[$number]) ? $all_instances[$number] : array();

				$was_cache_addition_suspended = wp_suspend_cache_addition();
				if ( $this->is_preview() && ! $was_cache_addition_suspended ) {
					wp_suspend_cache_addition( true );
				}

				$instance = $this->update( $new_instance, $old_instance );

				if ( $this->is_preview() ) {
					wp_suspend_cache_addition( $was_cache_addition_suspended );
				}

				/**
				 * Filters a widget's settings before saving.
				 *
				 * Returning false will effectively short-circuit the widget's ability
				 * to update settings.
				 *
				 * @since WP-2.8.0
				 *
				 * @param array     $instance     The current widget instance's settings.
				 * @param array     $new_instance Array of new widget settings.
				 * @param array     $old_instance Array of old widget settings.
				 * @param WP_Widget $this         The current widget instance.
				 */
				$instance = apply_filters( 'widget_update_callback', $instance, $new_instance, $old_instance, $this );
				if ( false !== $instance ) {
					$all_instances[$number] = $instance;
				}

				break; // run only once
			}
		}

		$this->save_settings($all_instances);
		$this->updated = true;
	}