Single logout for all multisite login
// Single logout from all sites
function clear_session_on_logout() {
$current_user = wp_get_current_user();
// get all sessions for user with ID $user_id
$sessions = WP_Session_Tokens::get_instance($current_user->ID);
// we have got the sessions, destroy them all!
$sessions->destroy_all();
}
add_action('clear_auth_cookie', 'clear_session_on_logout');