The PHP.net has announced the availability of the latest Release Candidate in the PHP 5.4.0 series - PHP 5.4.0 RC6:

The PHP development team announces the 6th release candidate of PHP 5.4. PHP 5.4 includes new language features and removes several legacy (deprecated) behaviours. Windows binaries can be downloaded from the Windows QA site. [...] The 6th release candidate focused on improving traits. Please test them carefully and help us to identify bugs in order to ensure that the release is solid and all things behave as expected.

You can download this latest release from the PHP QA site (Windows binaries) and test it on your local instance/applications. Any and all feedback about issues should be reported to either the QA mailing list or on the bug tracker. A complete list of updates is available in the NEWS file.