The code is tested on 2.1 and it works.

I have one question though. There is a note that says:

First, unless you iterate over all of the newTag objects and
call$em->persist($tag) on each, you'll receive an error from
Doctrine:

A new entity was found through the relationship
Acme\TaskBundle\Entity\Task#tags that was not configured to
cascade persist operations for entity...

I tested it with Doctrine 2.3.1 and I got no error.

@wouterj Are you adding new elements in the collection or only editing exsting ones ?

And are you cascading the persist on the relation ? If yes, it is indeed useless to persist explicitly each tag

Ping@wouterj! I'm waiting for answers on Stof's questions before moving on :)

Sorry for my delay on this. I need to finish some PRs now! :)

@stof was correct, the entity I used was cascading the persist action. (I just used your entity, so I wasn't aware of that)

@weaverryan I've updated the article, I think it's ready now

Nice work@wouter - I moved the new text further down in the article, but I have very few changes otherwise.

Tweaks at sha:ec49d58

Thanks!