Comparator.php

<?php

declare(strict_types=1);

final readonly class Comparator
{
    public static function compare(mixed $a, mixed $b): bool
    {
        /** @var \WeakMap<object, \WeakMap<object, bool>> */
        $comparedObjects = new \WeakMap();

        return self::doCompare($a, $b, $comparedObjects);
    }

    /**
     * @param \WeakMap<object, \WeakMap<object, bool>> $comparedObjects
     */
    private static function doCompare(mixed $a, mixed $b, \WeakMap $comparedObjects): bool
    {
        if ($a === $b) {
            return true;
        }

        if ($a === null || \is_scalar($a) || \is_resource($a)) {
            return false;
        }

        if (\is_array($a)) {
            if (!\is_array($b)) {
                return false;
            }

            if (\count($a) !== \count($b)) {
                return false;
            }

            if (array_is_list($a) && !array_is_list($b)) {
                return false;
            }

            foreach ($a as $key => $value) {
                if (!\array_key_exists($key, $b)) {
                    return false;
                }

                if (!self::doCompare($value, $b[$key], $comparedObjects)) {
                    return false;
                }
            }

            return true;
        }

        \assert(\is_object($a));

        if (!\is_object($b)) {
            return false;
        }

        // todo handle anonymous?
        if ($a::class !== $b::class) {
            return false;
        }

        $comparedToA = $comparedObjects[$a] ?? null;

        if ($comparedToA !== null) {
            if (isset($comparedToA[$b])) {
                return $comparedToA[$b];
            }
        } else {
            /** @var \WeakMap<object, bool> */
            $comparedToA = new \WeakMap();
            $comparedObjects[$a] = $comparedToA;
        }

        $comparedToA[$b] = true;

        return $comparedToA[$b] = self::doCompare(
            a: get_mangled_object_vars($a),
            b: get_mangled_object_vars($b),
            comparedObjects: $comparedObjects,
        );
    }

    private function __construct() {}
}