public function flow_verify(Flow $flow)
{
if (!$flow->isSessions("_onetimeticket") || $flow->inVars("_onetimeticket") !== $flow->inSessions("_onetimeticket")) {
$flow->vars("_onetimeticket", $flow->inSessions("_onetimeticket"));
throw new Exception("invalid ticket");
}
}