Symfony 2.0 entity form field not saving - php

Question

I am having issues saving the selections made in a entity form field with multiple=true.
The selections come through when $form->bindRequest($request) is called but don't persist in the database when flush is called.
Here is the relevant controller code:
$news_item = new News();
$form = $this->createFormBuilder($news_item)
->add('products', 'entity',
array('class' => 'AcmeDemoBundle:Product',
'multiple' => TRUE))
->getForm();
$request = $this->getRequest();
if($request->getMethod() == "POST") {
$form->bindRequest($request);
if($form->isValid()) {
$this->em->persist($news_item);
$this->em->flush();
}
}
I have checked the $news_item object after $form->isValid() and a count($news_item->getProducts()) returns the correct number of items. The $news_item itself is saved in the DB but the ManyToMany relationship isn't being saved.
Here are the entities for reference (clipped for brevity):
/**
* #ORM\Entity
* #ORM\Table(name="Product")
*/
class Product {
/*
* #ORM\Id #ORM\Column(type="integer")
*/
protected $id;
/**
* #ORM\ManyToMany(targetEntity="News", inversedBy="products")
*/
protected $news_items = null;
public function __construct() {
$this->news_items = new ArrayCollection();
}
}
/**
* #ORM\Entity
* #ORM\Table(name="News")
*/
class News {
/**
* #ORM\Id #ORM\Column(type="integer") #ORM\GeneratedValue
*/
protected $id;
/**
* #ORM\ManyToMany(targetEntity="Product", mappedBy="news_items")
*/
protected $products = null;
public function __construct() {
$this->products = new ArrayCollection();
}
}

Answer 1

I think you are missing $product->addNewsItem($news_item) and $news_item->addProduct($product) in your code this because in bi-directional associations (seems your case) you have to update the fields on both sides.
To avoid this you can set the cascade option on both sides of the association:
#ORM\ManyToMany(targetEntity="Product", mappedBy="news_items",
cascade={"persist", "remove"})
This way your code will work. You can choose the appropriate cascade options looking at here.

Answer 2

I'm not having the same problem that you are having, but I needed to be able to load FixtureData using similar entities. I was referred to this documentation: http://www.doctrine-project.org/docs/orm/2.1/en/reference/working-with-associations.html and I believe it's going to solve my problem. I hope this works for you too.
JS