This normalizer will normalize all properties of an object, regardless of visibility.

AggressiveObjectNormalizer.php

<?php

namespace App\Serializer;

use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;

/**
 * This normalizer will normalize all properties of an object, regardless of visibility.
 * It will not use methods, just reflection access to properties.
 * 
 * This is usually not a good idea, which is why it is disabled by default.
 * Use context: [AggressiveObjectNormalizer::class => true] to enable it.
 */
class AggressiveObjectNormalizer extends AbstractObjectNormalizer
{
    public function supportsNormalization(mixed $data, string $format = null, array $context = [] )
    {
        if (empty($context[__CLASS__])) {
            return false;
        }

        return parent::supportsNormalization($data, $format);
    }

    public function supportsDenormalization(mixed $data, string $type, string $format = null, array $context = [])
    {
        if (empty($context[__CLASS__])) {
            return false;
        }

        return parent::supportsDenormalization($data, $type, $format);
    }

    protected function extractAttributes(object $object, string $format = null, array $context = [])
    {
        $attributes = [];

        foreach ((new \ReflectionClass($object))->getProperties() as $property) {
            $attributes[$property->name] = true;
        }

        return array_keys($attributes);
    }

    protected function getAttributeValue(object $object, string $attribute, string $format = null, array $context = [])
    {
        return (new \ReflectionProperty($object, $attribute))->getValue($object);
    }

    protected function setAttributeValue(object $object, string $attribute, mixed $value, string $format = null, array $context = [])
    {
        (new \ReflectionProperty($object, $attribute))->setValue($object, $value);
    }
}