WordPress at a glance
function is not described

update_home_siteurl() WP 2.1.0

Flushes rewrite rules if siteurl, home or page_on_front changed.

No Hooks.

Return

Nothing (null).

Usage

update_home_siteurl( $old_value, $value );
$old_value(string) (required)
$value(string) (required)

Code of update home siteurl: wp-admin/includes/misc.php VER 5.0.3

<?php
function update_home_siteurl( $old_value, $value ) {
	if ( wp_installing() )
		return;

	if ( is_multisite() && ms_is_switched() ) {
		delete_option( 'rewrite_rules' );
	} else {
		flush_rewrite_rules();
	}
}