&reftitle.install; mbstring is an extended module. You must enable the module with the configure script. Refer to the Install section for details. The following configure options are related to the mbstring module. --enable-mbstring: Enable mbstring functions. This option is required to use mbstring functions. As of PHP 4.3.0, the option --enable-mbstring will be enabled by default and replaced with --with-mbstring[=LANG] to support Chinese, Korean and Russian language support. Japanese character encoding is supported by default. If --with-mbstring=cn is used, simplified chinese encoding will be supported. If --with-mbstring=tw is used, traditional chinese encoding will be supported. If --with-mbstring=kr is used, korean encoding will be supported. If --with-mbstring=ru is used, russian encoding will be supported. If --with-mbstring=all is added, all supported character encoding in mbstring will be enabled, but the binary size of PHP will be maximized because of huge Unicode character maps. Note that Chinese, Korean and Russian encoding is experimentally supported in PHP 4.3.0. --enable-mbstr-enc-trans : Enable HTTP input character encoding conversion using mbstring conversion engine. If this feature is enabled, HTTP input character encoding may be converted to mbstring.internal_encoding automatically. As of PHP 4.3.0, the option --enable-mbstr-enc-trans will be eliminated and replaced with mbstring.encoding_translation. HTTP input character encoding conversion is enabled when this is set to On (the default is Off). --enable-mbregex: Enable regular expression functions with multibyte character support.