The first release on the path to PHP7 has officially been released according to this new post on the main PHP.net website - PHP 7.0.0 Alpha 1.

The PHP development team announces the immediate availability of PHP 7.0.0 Alpha 1. This release marks the beginning of the PHP 7 major series. All users of PHP are encouraged to test this version carefully, and report any bugs and incompatibilities in the bug tracking system. PHP 7.0.0 Alpha 1 comes with new version of the Zend Engine with features. [...] For more information on the new features and other changes, you can read the NEWS file or the or the UPGRADING file for a complete list of upgrading notes. These files can also be found in the release archive.

As with other alpha PHP releases, you can download this preview version from the downloads page or windows.php.net/qa website for the binaries.