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.