public function touch()
{
if ($this->started !== true) {
throw new Exception\SessionNotStartedException('Tried to touch a session, but the session has not been started yet.', 1354284318);
}
// Only makes sense for remote sessions because the currently active session
// will be updated on shutdown anyway:
if ($this->remote === true) {
$this->lastActivityTimestamp = $this->now;
$this->writeSessionMetaDataCacheEntry();
}
}