cURL替代方案,支持Rackspace Cloudsites的TLS

We've developed a PHP cURL based plugin to connect to the Pathable API from Wordpress via Gravity Forms, testing the system it all worked perfectly, however in production the plugin is being hosted on a Rackspace Cloud site environment, apparently they're using curl/7.15.5 however we need curl/7.34 minimum to have support for TLS which is the only protocol that pathable support (SSL being insecure)

We cannot move to another host, we cannot update to the latest version of cURL so we need to re-build the plugin with another solution instead of cURL that's supported by Rackspace Cloud sites. I've spoken with their support but they're not aware of a specific solution so I'm wondering if anyone knows of an alternative that we could use?