I'm trying to be able to save to a text file

say if my text file contained:

define("NAMEOFAPP", "SOME APP");
define("KEYWORDS", "Keyword,Stuff,Etc");
define("DESCRIPT", "This is my description.");
define("SOMETEXT", "Blah Blah Blah");

I want to know how I can save over these. Not sure how to do this as I only know how to read, write, and append to text files.

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