WP_Widget_Search::update( array $new_instance, array $old_instance )

Source

File: wp-includes/widgets/class-wp-widget-search.php

public function update( $new_instance, $old_instance ) {
		$instance          = $old_instance;
		$new_instance      = wp_parse_args( (array) $new_instance, array( 'title' => '' ) );
		$instance['title'] = sanitize_text_field( $new_instance['title'] );
		return $instance;
	}