Beginning with PHP 4.2.0 these functions are enabled by default. For older versions you have to configure and compile PHP with --enable-ctype . You can disable ctype support with --disable-ctype .
PHP 的 Windows 版本已内建对此扩展的支持。不需要载入额外的扩展来使用这些函数。
Note: Builtin support for ctype is available with PHP 4.3.0.