Is there an existing implementation for generating TURN-server time limited credentials?

Question

i want to use a TURN-Server with time limited credentials, because the credentials will be used on client-side in plain text.

The process for the webserver is defined here:

https://code.google.com/p/rfc5766-turn-server/wiki/turnserver#TURN_REST_API

Is there an existing PHP implementation of that? The Name "TURN REST API" is irritating because the implementation is NOT for the TURN-Server itself.