Symfony\Component\PropertyAccess\PropertyAccessor::writeCollection PHP Method

    private function writeCollection($zval, $property, $collection, $addMethod, $removeMethod)
    {
        // At this point the add and remove methods have been found
        $previousValue = $this->readProperty($zval, $property);
        $previousValue = $previousValue[self::VALUE];

        if ($previousValue instanceof \Traversable) {
            $previousValue = iterator_to_array($previousValue);
        }
        if ($previousValue && is_array($previousValue)) {
            if (is_object($collection)) {
                $collection = iterator_to_array($collection);
            }
            foreach ($previousValue as $key => $item) {
                if (!in_array($item, $collection, true)) {
                    unset($previousValue[$key]);
                    $zval[self::VALUE]->{$removeMethod}($item);
                }
            }
        } else {
            $previousValue = false;
        }

        foreach ($collection as $item) {
            if (!$previousValue || !in_array($item, $previousValue, true)) {
                $zval[self::VALUE]->{$addMethod}($item);
            }
        }
    }