Thank you for your post!
I was unable to reproduce this behavior with a clean install of FileMaker Server 15.0.1 on OS X 10.11 El Capitan. Is it possible that the Operating System was updated after the installation of FileMaker Server 15.0.1 OR the FileMaker Server folder from a previous installation was not removed/renamed before this installation?
I think that I did an uninstall first, I usually do. Even so, it is
possible that the filemaker server folder from a previous installation
was not removed/renamed.
The strange thing is that the php.ini file that contains the erroneous
string is situated within a folder called "el capitan", see my first
post for the full path. I presumed that anything installed in that
folder would be new, not something from a previous installation.