[amosbatto]

ProcessMaker blocks anything placed in an unauthorized subdirectory of the /workflow/public_html directory, so /workflow/public_html/test/index.php will cause a problem. You need to place your code file directly in the /workflow/public_html directory and it should work. For example:
/workflow/public_html/mycode.php

Yes, I have filed a bug report about this and so far it its been ignored, so this is the only solution for now.