On the PHP.net site they've posted the announcement about the release of the latest Release Candidate for the upcoming PHP 7.3.x series: PHP 7.3.0RC4
The PHP team is glad to announce the next PHP 7.3.0 pre-release, PHP 7.3.0RC4. The rough outline of the PHP 7.3 release cycle is specified in the PHP Wiki.
[...] 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. Internal changes are listed in the UPGRADING.INTERNALS file. These files can also be found in the release archive.
As always, testing of this preview release (not intended for use in production) is appreciated and any bugs found should be reported. The source download can be grabbed from this download page and the Windows binaries are over on the Windows QA site.