Let's say you're a developer, like myself, and you have just updated to Apple's latest operating system (Yosemite or 10.10) and all of a sudden the Twilio PHP SDK stops working. And, it gives you an error something like this:
SSL: certificate verification failed (result: 5)
The problem disappears when you comment out the CURLOPT_CAINFO option, which makes it a bit more confusing. In other words, you can't use your own CA bundle/file. Others have also noted that it only really happens with certain certificate types, like wild-card domains (e.g., api.twilio.com doesn't work, for example).
Well, it seems to be a bug on the specific version of cURL, version 7.37.1, that Apple has bundled with their operating system. Version 7.37.0 and the latest version of cURL both work fine.
Check this out for all the details: http://sourceforge.net/p/curl/bugs/1404/
I haven't found a good way to fix it yet, myself, but the above link does offer some suggestions.