For PHP 4.3.3 or before, To enable that feature, you will have to supply either one of the following options to the LANG parameter of --enable-mbstring=LANG ; --enable-mbstring=cn for Simplified Chinese support, --enable-mbstring=tw for Traditional Chinese support, --enable-mbstring=kr for Korean support, --enable-mbstring=ru for Russian support, and --enable-mbstring=ja for Japanese support (default). To enable all supported encoding, use --enable-mbstring=all .