Ilia Alshanetsky has posted a new release announcement for the latest Release Candidate in the PHP 5.2.x series - PHP 5.2.2RC1.
The focus of this release is twofold, number one we are continuing to stabilize the language, with over 60 bug fixes. The second goal was to improve the security of the language through an internal audit as well as by addressing previously unknown bugs identified by MOPB. As you can imagine both these goals result in a rather extensive set of changes, so testing to make sure no new bugs or regressions were introduced is critical.
He stresses the importance of testing this release because of a real push to get this release (with all of its bugfixes) out as soon as possible.