Those characters are part of the UTF-8 charset.
PHP is known to have some problems with multibyte characters, since 1 char in PHP is represented on 1 byte.

The solution is fairly simple: change the header and content type encoding to utf-8:
Code:
header('Content-Type: text/html; charset=utf-8');
...
and later:
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
...
Hope this helps.