For the pinky stack there is a default Procfile generated by the buildpack. You only need to override the default Procfile when you want to start some workers, were you also need to define the web process to start.
You can fine more info at https://github.com/cloudControl/buildpack-php#custom-procfile.
The command to add the worker also needs to be modified, see https://www.cloudcontrol.com/dev-center/Add-on%20Documentation/Data%20Processing/Worker.