The main PHP.net site has posted the announcement about the release of the latest Release Candidate for the upcoming PHP 7.3.0 series: PHP 7.3.0RC3.
The PHP team is glad to announce the next PHP 7.3.0 pre-release, PHP 7.3.0RC3. The rough outline of the PHP 7.3 release cycle is specified in the PHP Wiki.
For source downloads of PHP 7.3.0RC3 please visit the download page. Windows sources and binaries can be found on windows.php.net/qa/.
For more information on what changed and how to migrate to this new version, check out the NEWS and UPGRADING files respectively. The next release would be RC4, planned for October 25th.