On the PHP.net site they've posted the announcement about the release of the latest alpha in the PHP 7.2.0 series: PHP 7.2.0 Alpha 3

The PHP development team announces the immediate availability of PHP 7.2.0 Alpha 3. This release contains fixes and improvements relative to Alpha 2. All users of PHP are encouraged to test this version carefully, and report any bugs and incompatibilities in the bug tracking system.

This release is intended for development only and is not to be used in production. The NEWS section for this release contains updates that are new to this alpha, mostly around bugfixes (but some new features are slowly working in for the final 7.2.0 release). As always you can download the source packages from the QA downloads page or grab the Windows packages for this alpha from the Windows QA site.

PHP.net has announced the release of PHP 5.5 alpha3, the latest alpha in this upcoming release. This is only a preview release and should not be considered (in any way, shape or form) as usable in production.

The PHP development team announces the release of PHP 5.5.0alpha3. This release adds few features and fix some bugs from alpha2. All users of PHP are encouraged to test this version carefully, and report any bugs in the bug tracking system.

There's a few new things that have come with this update including the "Generator::throw()" method, a few additional cURL methods, Max-Age attribute support in setcookie and some bugfixes in mysqlnd and the PHP core code (see here for the full list). Please download this latest alpha and test it out in your application. Windows binaries are here.

The PHP development group has officially released the alpha3 of PHP 5.4 as ready for testing. Rasmus Lerdorf comments:

PHP 5.4 alpha3 is available for testing now. Please give us a hand and compile it on your platform and run a "make test". Download it from http://qa.php.net and you can see the changes in the NEWS file at http://t.co/bBVGj8P

Updates in this alpha include the shortened array syntax, binary numbers format, support for the "Class::{expr}()" syntax, removal of magic quotes related features, a change to include E_STRICT in E_ALL and several others. Head over to the PHP QA site and download this latest version to test in your environment. Remember, environments are unique, so the more test results the better - it helps make for a better quality end result.