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.
The Windows version of PHP has built-in
support for this extension. You do not need to load any additional
extensions in order to use these functions.
Note:
Builtin support for ctype is available with PHP 4.3.0.