Ilia have just announced on his blog the availability of PHP 5.2.1 RC1 for testing. You can get tarballs php-5.2.1RC1.tar.bz2, php-5.2.1RC1.tar.gz or binaries for windows users from php-5.2.1RC1-Win32.zip thanks to Edin. Testing this release candidate is highly suggested to help finding any possible bugs or other leaks. Ilia noted on his blog :

This release is primarily aimed at improving the stability of the language and finalization of features introduced in 5.2.0. There are over 70 different bug fixes, a great deal of performance improvements for Windows users, corrections to the memory manager and the improvement in the filter functionality. I’d like to ask everyone to try this release out and let us know if you come across any issues and/or regressions.