Problem with iso8859-2 characters in combo

I’m trying to make something very similar to that

Everything is working very fine except one thing, when you write in combo mask with character with accent (from iso8859-2 set) like ć ś ż ź there is no that chracters inside loadCombo.php, there is some characters in $_GET[“mask”] but in IE it’s latin equivalent (with no accent), in chrome it’s “something” (mainly A with double dot above).

The question is - it is possible to make it working? the problem is in transwer mask
through $_GET (url)? urlencode/urldecode doesn’t help maybe that url is not encoded?