&reftitle.install;

`mbstring` is a non-default extension. This means it is not enabled by default. You must explicitly enable the module with the `configure` option. See 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.

  libmbfl is necessary for `mbstring`. libmbfl is bundled with `mbstring`. Prior to PHP 7.3.0, if libmbfl is already installed on the system, `--with-libmbfl[=DIR]` can be specified to use the installed library.

- `--disable-mbregex`: Disable regular expression functions with multibyte character support.

  Oniguruma is necessary for the regular expression functions with multibyte character support. As of PHP 7.4.0, pkg-config is used to detect the libonig library. Prior to PHP 7.4.0, Oniguruma was bundled with `mbstring`, but it was possible to build against an already installed libonig by passing `--with-onig[=DIR]`.

  It is possible to disable the multibyte regex backtrack check by specifying `--disable-mbregex-backtrack`.