In reply to Drew Jaynes.

Oow that is so easy to say. I have tested this on different servers now. All the same issue. There are several threads on the fora now reporting the issue. Even on wordpress.org https://wordpress.org/support/topic/cant-edit-main-theme-php-files-after-upgrading-to-4-9

So not being able to edit a php file is a feature. That is a lot of crap. Before answering or replying please investigate a issue properly.

I can edit the css style sheet with the editor. But not any php file. This is a BUG !