Content-Disposition header and Cyrillic filename

header('Content-Disposition: attachment; filename="cyrilic_filename.ext"开发者_开发技巧');

is it possible somehow to set that it's an UTF-8 name? Or I'm to convert filename to ASCI?

Yes, it's possible, but doesn't work for all browsers yet. See http://greenbytes.de/tech/tc2231/, http://greenbytes.de/tech/webdav/rfc5987.html, and http://greenbytes.de/tech/webdav/draft-ietf-httpbis-content-disp-latest.html.