The PHP development group has posted the official release announcements for the latest versions in the PHP 5.6.x and 5.5.x series: PHP 5.6.24 and PHP 5.5.38.

The PHP development team announces the immediate availability of PHP [5.6.24 and 5.6.38]. This is a security release. Several security bugs were fixed in this release. All PHP 5.6 users are encouraged to upgrade to this version.

They also have a quick note that this release for the PHP 5.5.x series is the last in the branch as laid out by the release schedule. Future updates on this branch will only be made if there are major security issues found. Otherwise developers are encouraged to upgrade to the latest versions (5.6.x at the least but really PHP 7.x would be better). You can get these latest releases either from the main downloads page (source) or from windows.php.net for the Windows binaries.