Modifying Constants, Functions, Classes, and Methods
works with all releases of PHP 4 and PHP 5. No special requirements are
Custom Superglobals are only available in PHP 4.2.0 or later.
Sandboxing requires PHP 5.1.0 or later, or
PHP 5.0.0 with a special TSRM patch applied.
Regardless of which version of PHP is in use it must be compiled with the
See the README file in the runkit package for additional information.