Since Doctrine 3, ClassUtils::getClass() has been removed.

Here's my current replacement.

use Doctrine\Persistence\Proxy;

// ...

    public static function getRealClass(object|string $entityOrClass): string
    {
        $class = is_object($entityOrClass)
            ? $entityOrClass::class
            : $entityOrClass;

        if (is_subclass_of($class, Proxy::class, true)) {
            return get_parent_class($class);
        }

        return $class;
    }