Can I use strings with some unicode characters as array keys?

Question to someone who's familiar with how arrays are implemented in PHP. I've tried asking this on stackoverflow.com, but it looks like I need to ask this one to people familiar with PHP source. PHP manual says that one should only use strings or integers as array keys. Also I know that PHP doesn't speak unicode yet. So - I was just wondering - when unicode characteres are used in array key - does PHP strips them or affects them in any way? or does iPHP simply treats keys as binary string, the end of the story? Thank you!