What's the server OS?
If it's Windows, you'll not be able to access files under a UTF-8-encoded filename, because the Windows implementation of the C IO libraries used by PHP will only talk in the system default code page. For Western European installs, that's code page 1252. You can convert a UTF-8 string to cp1252 using iconv:
$winfilename= iconv('utf-8', 'cp1252', $utffilename);
(utf8_decode
could also be used, but it would give the wrong results for Windows's extension characters that map to the range 0x80-0x9F in cp1252.)
Files whose names include characters outside the repertoire of the system codepage (eg. Greek on a Western box) cannot be accessed at all by PHP and other programs using the stdio. There are scripting languages that can use native-Unicode filenames through Win32 APIs, but PHP5 isn't one of them.
And of course the step above shouldn't be used when deployed on a different OS where the filesystem is UTF-8-encoded. (ie. modern Linux.)
If you need to seamlessly cross-server-compatible with PHP, you'll have to refrain from using non-ASCII characters in filenames. Sorry.
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