Array Sorting Blues....

I'm new to PHP so please be gentel with me.
I have a 2 dimensional array where one col contains a Unix style date and the other contains a filename. I read through a directory to get this info. I can load the array and print it out just fine, but I can't seem to sort it using any of the sort functions! I want to reverse sort them, since they are news stories that I want to display in the correct order by date. When I try to sort I get a "Warning: Cannot compare arrays or objects" message. I have the feeling it's something stupid on my part but can't find any good examples anywhere.

Anyone have an idea about this?

P.S. I know a database would solve this but sadly it's not an option for me right now URL