Beginning with PHP 4.3.0 these functions are enabled by default.
For older versions you have to configure and compile PHP with
--enable-tokenizer. You can disable
tokenizer support with --disable-tokenizer.
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:
Built-in support for tokenizer is available as of PHP 4.3.0.