PHP 8.6 locks its feature set as RC3 ships ahead of November GA

PHP 8.6.0 RC3 went out on 6 October, and php.net’s own notes describe it as bug-fix and memory-safety corrections only, across 21 areas, with no new features and no CVEs. That is expected this late in the cycle: the feature freeze already passed, so RC3 is purely about stability before release.

The feature list locked in at freeze includes partial function application, which lets you pre-bind some arguments of a call with ? as a placeholder for the ones you’ll supply later, a new clamp() function for constraining a value to a range, a Duration class, readonly properties that can now carry default values, and optimisations to closures created from first-class callables. PHP’s release wiki has general availability targeted for 19 November.

function add(int $a, int $b): int {
    return $a + $b;
}

$addFive = add(5, ?); // ? marks the argument to fill in later

Why it matters: if you maintain a library or framework that wants day-one 8.6 support, RC3 is the build to test against now — the feature set is frozen, so anything that works against RC3 should carry through to the final release on 19 November.