I have deployed several PHP apps on GAE standard environment, all working fine.
Now I\'m deploying a new app, which on the local server provided by the gcloud
After several hours of testing, I finally realized what the problem was.
In GAE when declaring a certain path static, it is then interpreted as a non-code path. All files within that path are therefore not accessible by the scripts running on the PHP environment with require or include and they are not shown in the deployed code debugger.
For this reason, I have placed all static files in a sub-folder (www), and non static files to be required by PHP scripts under another subfolder.