I've seen this kind of question before, but I have to ask again. As far as I can tell I'm subscribed to Bing (full, not Web Only) properly. Still, every attempt to run the example PHP script fails with Connection Refused.
Putting the exact request (as echoed by the PHP script on the failed page) into my browser and supplying the same accountKey at the prompt returns a proper result.
At the risk of redundancy I will reproduce the script here, in case there's something I'm still missing: