On the PHP.net site they've posted an announcement about the latest Release Candidate of the language for the PHP 7.2.x series: PHP 7.2.0 Release Candidate 2.

The PHP development team announces the immediate availability of PHP 7.2.0 RC2. This release is the second Release Candidate for 7.2.0. All users of PHP are encouraged to test this version carefully, and report any bugs and incompatibilities in the bug tracking system.

[...] For more information on the new features and other changes, you can read the NEWS file, or the UPGRADING file for a complete list of upgrading notes. These files can also be found in the release archive.

You can download this latest pre-release version from either the source downloads or Windows site for the Windows binaries. The next release candidate will be posted on September 28th according to the release schedule with a few more to follow to work out all of the potential issues in this next major release of the language.