short type codes for use in array conversion

I found a method for converting javascript arrays to PHP arrays here: "http://aspn.activestate.com/ASPN/Cookbook/PHP/Recipe/414334" and would like to expand the list of types the function knows about. It looks like 's' = string, 'a' = array but 'i' for integer and 'n' for number don't work. Is there a list of type codes somewhere on the php site? I did a search but apparently didn't hit upon the correct phrase as all searches came up with zero results. Thanks for any help Ken