php - Symfony2 serialize entity object to session

Question

I want to save one of my entity objects into the session, but as I'm doing so, I'm getting the following two errors:

Exception: SymfonyBundleFrameworkBundleDataCollectorRequestDataCollector::serialize() must return a string or NULL

and

ErrorException: Notice: serialize(): "id" returned as member variable from __sleep() but does not exist in /var/www/clients/client71/web256/web/_dev_fd/kkupon/vendor/symfony/src/Symfony/Component/HttpKernel/DataCollector/DataCollector.php line 29

My code goes like this:

$offer = $this->getEntityManager()->getRepository('KkuponMainBundle:Offer')->find($offer_id);
$request->getSession()->set('offer', $offer);

How could I get it right?

Thank you.

UPDATE With Rowgm's help I could fix this problem by setting properties protected instead of private. The only problem I have is after reading the entity from the session the EntityManager does not know about it, and if I add the object(from the session) to another object(there is OneToMany relationship between them), it won't work.

<?php
$offer = $this->get('session')->get('offer');
$coupon = new Coupon();
$coupon->setOffer($offer);
$this->em->persist($coupon);
$this->em->flush();

This raises an error, because coupon has an object property which according to the EntityManager is not in the database(actually it is in the DB, I put to the session from the DB).

<?php
$offer = $this->get('session')->get('offer');
echo $this->em->getUnitOfWork()->isInIdentityMap($offer) ? "yes":"no"; //result: no

One solution can be: $offer = $this->em->merge($offer);

But this doesnt seem to be the best one. I'd like my EntityManager to perceive entity objects stored in session without telling it each time. Any idea?

Answer 1

You can serialize any entity by setting all their properties and relationships from private to protected.

You could have a common issue with symfony2, even if you have set all properties to protected: You have to re-generate the proxies of those entities you have changed. To do so, simply clear the cache. For dev enviroment:

app/console cache:clear

It works even if "it contains many foreign objects and even ArrayCollections of foreign entities" as you said.