Can one .PHP file edit another?

Question

So I have a file for constants. I want to let user define them and then edit my .php filr with that global constants (not xml - real PHP file )

With such code for exampl

Answer 1

Not talking about security, one simple way is that you can read the php file using reading functions like file_get_contents and once you have the contents, you should show them in some textarea where your users could edit it. Once they edit it and submit the form, you should update the info.