Problem:
When creating a symlink to a php page, I get a 500 error. I am able to use symlinks to other files and folders fine.
Solution:
We do not allow symlinking PHP files on our server, as this could cause security issues. There is not a way around this unfortunately, even if you parse HTML as application/x-httpd-php. You will be able to symlink to other files and folders, only PHP should give you the error.