The initialization code for the fallback conversion was checking for the
presence of the wrong function. mb_strtoupper and mb_strtolower are only
present starting in 4.3.0, so the case arrays were not being loaded when
the extension was detected as present and the fallback converter failed.
$wgInputEncoding = "UTF-8";
$wgOutputEncoding = "UTF-8";
-if (function_exists('mb_internal_encoding')) {
+if( function_exists( 'mb_strtoupper' ) ) {
mb_internal_encoding('UTF-8');
} else {
# Hack our own case conversion routines