I received the following notice from Zend:
Migrate your PHP 4-based applications to PHP 5 before August.
Migrating applications can be a painful process but less so if you make the transition on your own terms. Creating a transition plan for your PHP 4 based applications before August 31, 2008 when community support for PHP 4 runs out, is critical. To help you, Zend offers a complete set of services, from training to consulting, to help you plan, transition or migrate your PHP 4 applications.
They also have a white paper on making the change:
http://static.zend.com/topics/White-paper-PHP4-PHP5.pdf
I still have a lot of legacy scripting on old websites and I'm probably not the only one.