Connecting to a proxy with HTTPS in PHP5.6.8

Question

Modern browsers support connecting to a secure/spdy proxy, it can be configured in a PAC file:

return PROXY proxy.example.com:8001

for an http proxy or

return HTTPS secure-proxy.example.com:8001

for a secure proxy.

The server's successfully connected to on Firefox and Chrome.

Now I'm trying to find a way to connect to this proxy with PHP but no luck so far, I wonder if it's possible at all and how. AFAIK, cURL seems to be out of the question: How to connect to a secure (https) proxy with curl and php?

Thanks