This is a major bug of XAMPP. Millions of people use files names that are not in English but by default, XAMPP PHP does not support this essential feature.
See related articles in:
http://stackoverflow.com/questions/9659600/glob-cant-find-file-names-with-multibyte-characters-on-windows
http://www.rooftopsolutions.nl/blog/filesystem-encoding-and-php
How do I activate PHP files names in other language after I already installed XAMPP?