Modifying Constants, Functions, Classes, and Methods works with all releases of PHP 4 and PHP 5. No special requirements are necessary.

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 --enable-maintainer-zts option. See the README file in the runkit package for additional information.