--enable-mbstring: Enable mbstring functions. This option is required to use mbstring functions.
libmbfl is necesarry for mbstring. libmbfl is bundled with mbstring. If libmbfl is already installed on the system, --with-libmbfl[=DIR] can be specified to use the installed library.
As of PHP 4.3.0, mbstring extension provides enhanced support for Simplified Chinese, Traditional Chinese, Korean, and Russian in addition to Japanese.
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.
Note: As of PHP 4.3.4, all supported encoding by libmbfl is enabled with --enable-mbstring.