As is mentioned in this new post on the PHP.net site, the first release candidate of the PHP 7.2.0 pre-release cycle has been officially released: PHP 7.2.0 RC1.

The PHP development team announces the immediate availability of PHP 7.2.0 Release Candidate 1. This release is the first 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.

Changes in this release include updates in the GD image handling, PCRE's UTF-8 handling, SQLite driver update, a CURL issue wth OpenSSL detection and Internationalization changes. You can download this pre-production release from either the source download site or the Windows QA site for the Windows binaries.