Resulting from a conversation among developers at this year's PHP Quebec 2008 conference, a new event has been created to help test PHP against as many different configurations as it can be - TestFest.
The TestFest is an event that aims at improving the code coverage of the test suite for the PHP language itself. As part of this event local UG are invited to join the TestFest. All it takes is a local organizer to spear head the event and to get others involved in writing phpt tests. The submissions will then be reviewed by members of php.net before getting included in the official test suite.
The even will be announced sometime in March and its hope is to get as many people in the community involved to improve the language. There'll also be a raffle to give away 10 of the stuffed elePHPants as well as, for the ones who are "test worthy" and seem able to write up good tests on their own - commit CVS access to php.net as well as an official php.net account.
For more details on the event, check out this page on the (new) PHP.net wiki.