The PHP development group has announced the release of the latest versions in all three major versions of PHP currently supported: PHP 5.6.7, 5.5.23 and 5.4.39. These releases are bugfix only with several security updates included.
The PHP development team announces the immediate availability of [these new versions]. Several bugs have been fixed as well as CVE-2015-0231, CVE-2015-2305 and CVE-2015-2331. All PHP [5.6, 5.5 and 5.4] users are encouraged to upgrade to this version.
As always, you can get the latest released for each of these versions from the main downloads page (for Windows users on windows.php.net) and if you'd like to see the other changes besides the security-related fixes check out the full Changelog.