Manual:$wgShellLocale

Details
Locale for, to work around http://bugs.php.net/bug.php?id=45132.

For Unix-like operating systems, set this to a locale that has a UTF-8 character set. Only the character set is relevant.

See [http://msdn.microsoft.com/en-us/library/0h88fahh%28VS.85%29.aspx here] for a list of Locale IDs (LCID).