PHP 8.6 RC3 Released as Drupal Compatibility Work Continues

Developers can test PHP 8.6.0 Release Candidate 3 (RC3), which the PHP development team released on 8 October 2026 as the language approaches its planned November stable release. The team describes RC3 as a testing build and advises against using it in production.

Drupal core contributors are testing PHP 8.6 through continuous integration, but the project's published PHP requirements do not yet list the version as supported. Instead, Drupal.org directs readers to an open compatibility tracking issue covering failures and upstream dependency changes. Successful tests against individual development builds do not establish official production support.

Drupal core contributor Andrey Postnikov opened the tracking issue on 5 July 2026 after early PHP 8.6 testing exposed incompatibilities. One failure involved generated classes in the phpspec/prophecy testing library, where a destructor returned a value during a Drupal database cache test. PHP 8.6 introduces a deprecation for returning values from constructors and destructors, requiring affected code and libraries to change.

Several upstream projects have already addressed related problems. A PEAR Archive_Tar correction removing return values from constructors and destructors was merged in July, while Symfony merged PHP 8.6 deprecation fixes in August. A separate Prophecy pull request addressing PHP 8.6 remained open when reviewed. These changes are part of the wider compatibility effort and were not introduced by RC3 itself.

Compatibility work was still producing new findings in October. On 1 October, Postnikov reported a PHP 8.6 deprecation in guzzlehttp/promises affecting tests of Drupal's Announcements module. The warning concerned the use of is as a class name, which PHP 8.6 deprecates. The issue is another example of upstream changes being tracked; it does not establish a production failure in Drupal.

Postnikov reported a successful Drupal test pipeline during the initial testing period in July, following adjustments to the PHP 8.6 testing environment. The tracking issue nevertheless remains open, with contributors expected to create follow-up issues when subsequent builds expose failures. A passing pipeline is therefore one checkpoint in compatibility testing rather than confirmation that all remaining problems have been resolved.

The PHP 8.6 release schedule lists RC4 for 22 October, RC5 for 5 November and general availability for 19 November 2026. The release-candidate numbering follows a packaging issue that caused RC1 to be skipped; RC2 was released on 24 September. All remaining dates are planned milestones and may change.

For Drupal site operators, the immediate distinction is between compatibility testing and supported production use. Drupal 12 requires PHP 8.5, but that requirement does not automatically establish support for PHP 8.6. Developers can test PHP 8.6 in isolated environments and report failures, while production installations should continue using PHP versions supported by their installed Drupal release.

Further information is available in the official PHP RC3 announcement and Drupal's PHP 8.6 compatibility tracker.