This project started as drop-in replacement for the legacy Plivo framework (the open source platform, not their current commercial solution); the underlying stack of choice is ReactPHP, excellent for any asynchronous applications.

Given the complex nature of VoIP integrations, a sample application sandbox is also available.

This might be of interest if you’re looking for Twilio, Plivo, Nexmo etc. alternatives and willing to run your media servers (FreeSWITCH) and your SIP vendors of choice.