PHP - File handling/manipulation question

Alright, I plan on making a news updating program for my website so I can stop using blogger.com (even though it works really well if you tweak it out with a bunch of PHP.) It seems like it will be easy enough to do this myself, but I would also like to take a stab at doing the autoarchiving and stuff. One thing I was wondering is if I saved every news update as a seperate text file, would that be a lot slower than saving all the news updates into ONE text file (possibly 1 month/text file or something.) So in short - is it faster to save everything to one file than it would be to save stuff to different files. If you have any thoughts, just throw em out, I would appreciate it.

Thanks!