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<?php declare(strict_types=1); namespace Repro; class CycleValue { private ?\stdClass $cycleRef; public function __construct() { // make self cyclically referenced $this->cycleRef = new \stdClass(); $this->cycleRef->x = $this; } public function __destruct() { echo "d\n"; $this->cycleRef->x = null; $this->cycleRef = null; } } class CycleWithDestructorForGcMonitoring { private \Closure $destructorFx; private \stdClass $cycleRef; public function __construct(\Closure $destructorFx) { $this->destructorFx = $destructorFx; $this->cycleRef = new \stdClass(); $this->cycleRef->x = $this; } public function __destruct() { ($this->destructorFx)(); } } $ref = \WeakReference::create(new CycleValue()); $isSecondGcRerun = false; // https://github.com/php/php-src/commit/b58d74547f $createMonitorGcFx = static function () use ($ref): void { $destructorFx = static function () use ($ref): void { echo "gc\n"; var_dump($ref->get() !== null); var_dump($ref->get() !== null); }; new CycleWithDestructorForGcMonitoring($destructorFx); }; $createMonitorGcFx(); gc_collect_cycles(); /**/if (PHP_VERSION_ID < 80100) { gc_collect_cycles(); } echo "done\n";