I have not tried to create a UTF-8 file with PHP code (and I have not tried to update one also).
Anyway - I belive it can be done - but I am not sure. I dunno.
I will probaly need it too - when I write the admin module for my website. I will want to give the admin (or translator) the opportunity to change the multilingual variables via web interface (browser).
I'm afraid that it might end up on using the DB after all. (But I'd better not use the DB for translation - we'll see) I dunno.
I am going to deal with this queston soon (maybe next week). Right now I'm dealing with templates (phplib). seeya.