Apache, standard “Apache httpd (PHP, HTML)” runner (the problem occurs with and without XDebug turned on). PHP project pulled from GitHub, no changes to the config other than pointing all requests at a router entry script. Very standard setup, in part because this was a workspace designed for our documentation on getting a dev installation up and running on Cloud9.
After a number of refreshes, it usually “finds” the site and works for awhile.
I had realized this was a semi-old thread, and thus possibly unrelated to my issue, so I also opened a new thread. Sorry for the duplicate; I could not decide which was the right way to go (opening a new topic or replying to this one).
The one change to Apache was to edit /etc/apache2/sites-enabled/001-cloud9.conf and add the following (in the appropriate place, this is from the notes I took as I made the changes):
Alias / /home/ubuntu/sites/dev.php/
Require all granted
Allow from all
Also, two packages were added with:
sudo apt update
sudo apt install php5-imagick ffmpegthumbnailer
Finally, a MySQL user and database were created.