I started getting these recently.
I saw the problems with the cert.pem in '15, and I've updated it. no luck.
This was working code, so it looks like it's a cert problem, but I have to solution. Any ideas? thanks,
// Create the subscription.
$request = new AuthorizeNetARB;
$response = $request->createSubscription($subscription);
$subscription_id = $response->getSubscriptionId();
$out = array(
'message' => "done",
'subscriptionid' => $subscription_id,