As was previously mentioned by Christopher Jones, the PHP 5.3 branch is now under a feature freeze. Lukas Smith has posted a few more details about the upcoming release.

Last thursday was the begin of the feature freeze phase. Well its not really a hard feature freeze in the sense that we still have plans for a few new features and tweaks, but it means the end of the "maintainers freedom" that usually rules PHP development more or less.

New features will have to go through either him or Johannes to be included and they are doing their best to get the alpha 1 release of this new version out by July 31st.

Lukas is also trying a more unconventional approach to bug fixes to try to get the major ones knocked out first - posting them as a comment to this blog post. So far, no comments on bugs have been added, but there are a good number to get through. To help narrow it down he's also put out a plea to developers out there to help validate current bugs to potentially knock off a few of the ones that can be marked bogus.