Getting Cloud9 to accept a standard Google App Engine PHP project


Since since Cloud9 accepting a standard Google App Engine PHP project seems so obvious a requirement, is the fact I’m failing due to my error?

I set up a workspace using defaults here possible and from Google c9 has taken these two files but Run Project fails with:

Running mvn gcloud:run and watching for changes...
not a maven project: missing pom.xml

  Project not supported

  Thanks for trying out Cloud9 for Google App Engine. At the moment, only a few
  well-known project configurations can be run and deployed through the Cloud9
  interface. It looks like this project uses a language or format we do not
  understand yet.

  To get started, delete all files in your project and try again. You can also
  create a new and empty Google Cloud Platform project and open it in Cloud9.

  This release of Cloud9 supports the following project configurations:

  java  Java Web Application with JSP, Servlets (run local, deploy)
        App Engine Java Managed VM

Process exited with code: 201

How do I get c9 to recognise this Google project files?