wp_switch_roles_and_user() WordPress Function

function wp_switch_roles_and_user( $new_site_id, $old_site_id ) {
	if ( $new_site_id == $old_site_id ) {
		return;
	}

	if ( ! did_action( 'init' ) ) {
		return;
	}

	wp_roles()->for_site( $new_site_id );
	wp_get_current_user()->for_site( $new_site_id );
}
Uses	Description
wp-includes/class-wp-roles.php:WP_Roles::for_site()	Sets the site to operate on. Defaults to the current site.
wp-includes/capabilities.php:wp_roles()	Retrieves the global WP_Roles instance and instantiates it if necessary.
wp-includes/pluggable.php:wp_get_current_user()	Retrieve the current user object.
wp-includes/plugin.php:did_action()	Retrieves the number of times an action has been fired during the current request.