have you thought of simply commenting out where that function is called and/or located within your code, and than creating a text file log of the files you have altered and which line the changes started on?
This way you will have a quick and easy to access path to all of your changes. Furthermore, if you just place comment brackets around the code, a matter of 4 backspaces will return the original code.
for example:
*/
the function would be located in here, now ignored by PHP
/*
to preserve simplification, place your alternate function right beneath, or just a comment explaining what youve done for future references...
Hopefully thats somewhat on track with what you're aiming to accomplish, good luck!