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 been researching this for couple of hours but my C level is still
a bit low.
PHP manual says that one should only use strings or integers as keys.
Also  I know that PHP doesn't speak unicode yet.
So - I was just wondering - when unicode characteres aare 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?

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