As explained in the [restrictions for entity classes in the manual](http://www.doctrine-project.org/documentation/manual/2_0/en/architecture#entities),
it is usually not allowed for an entity to implement `__wakeup` or `__clone`, because Doctrine
makes special use of them. However, it is quite easy to make use of these methods in a safe way
by guarding the custom wakeup or clone code with an entity identity check, as demonstrated in the following sections.

++ Safely implementing __wakeup

To safely implement `__wakeup`, simply enclose your implementation code in an identity check
as follows:

    [php]
    class MyEntity
    {
        private $id; // This is the identifier of the entity.
        //...
        
        public function __wakeup()
        {
            // If the entity has an identity, proceed as normal.
            if ($this->id) {
                // ... Your code here as normal ...
            }
            // otherwise do nothing, do NOT throw an exception!
        }
        
        //...
    }

++ Safely implementing __clone

Safely implementing `__clone` is pretty much the same:

    [php]
    class MyEntity
    {
        private $id; // This is the identifier of the entity.
        //...
        
        public function __clone()
        {
            // If the entity has an identity, proceed as normal.
            if ($this->id) {
                // ... Your code here as normal ...
            }
            // otherwise do nothing, do NOT throw an exception!
        }
        
        //...
    }

++ Summary

As you have seen, it is quite easy to safely make use of `__wakeup` and `__clone` in your entities
without adding any really Doctrine-specific or Doctrine-dependant code.

These implementations are possible and safe because when Doctrine invokes these methods,
the entities never have an identity (yet). Furthermore, it is possibly a good idea to check
for the identity in your code anyway, since it's rarely the case that you want to unserialize
or clone an entity with no identity.