get-comparable-array.php

<?php
abstract class AbstractProperties extends \ArrayObject implements PropertiesInterface
{
    final public function getComparableArray() : array
    {
        return $this->getComparableArrayRecursive([]);
    }
  
    final protected function getComparableArrayRecursive(array $stack)
    {
        $hash = spl_object_hash($this);
        $stack[$hash] = $this;
        $array = $this->getArrayCopy();
        array_walk_recursive($array, [$this, 'makeValueComparable']);
        unset($stack[$hash]);
        return $array;
    }

    final protected function makeValueComparable(&$value, array $stack) : void
    {
        if ($value instanceof static) {
            $hash = spl_object_hash($value);
            if (($stack[$hash] ?? null) === null) {
              $value = $value->getComparableArrayRecursive($stack);
            }
        }
    }
}