PHP 8.6 RC2 Is Out: Release Roadmap to November 2026 and the Key Changes at a Glance

What's new in PHP 8.6?

PHP 8.6.0 RC2 was tagged on September 23, 2026, about eighteen hours after RC1 the day before. RC2 contains only three fixes over RC1: a resource leak in the CLI development server for requests to static files, corruption of session state when strict mode rejects a supplied session ID, and a previously silent failure of unserialize('') instead of a proper error.

On the feature side, PHP 8.6 brings several new language additions: partial function application lets you pre-fill individual function arguments to create new callables, for a more functional programming style. The built-in clamp() function constrains a value to a given range. There's also a new Time\Duration value type, an Io\Poll polling API, default values for readonly properties, and extended error handling for streams plus chunked fetching for PostgreSQL.

Why it matters

PHP's annual release rhythm has been stable for years: 8.2 in November 2022, 8.3 in November 2023, 8.4 in November 2024, 8.5 on November 20, 2025. PHP 8.6 follows the same pattern; the stable release is expected in November 2026. For TYPO3 and Sylius operators, that gives a predictable point in time to test compatibility before hosting providers and distributions switch to 8.6 as the default version.

More relevant to most teams than the new features are the deprecations that ship with PHP 8.6: passing objects where arrays are expected, the legacy functions is_double() and is_long(), the metaphone() function, and using "namespace" as a class constant name. Deprecations are typically the first thing that bites when moving to a new major version, far more often than the new features themselves.

What you should do now

There's time for a structured test before the stable release in November, no rush for a production switch:

# Install PHP 8.6 RC2 locally or in a test container
docker run --rm -it php:8.6.0RC2-cli php -v

# Check your own dependencies for PHP 8.6 compatibility
composer why-not php:^8.6

# Run static analysis with your current PHPStan/Psalm configuration
vendor/bin/phpstan analyse --level=max

Check in particular for calls to is_double(), is_long(), and metaphone() in your own code and in dependencies, and look for places where objects are passed to array parameters. For TYPO3 installations, it's worth checking the TYPO3 compatibility matrix once it's updated for 8.6; TYPO3 LTS versions typically support new PHP major versions only some time after their stable release.

Conclusion

PHP 8.6 follows the project's established annual rhythm, with a modest feature set and the usual deprecations. The real preparation work lies less in the new features than in testing against the release candidates early and cleaning up deprecated function calls before the stable release ships in November 2026.

Sources

• LinuxCompatible: PHP 8.6.0 RC2 Released Days After RC1 Ahead of November Stable Launch
• LinuxCompatible: PHP Releases Five Versions at Once, Includes 8.6.0 RC1 and 8.5.11
• PHP.Watch: PHP 8.6 — What's New and Changed