You have incorrect mapping information for the Category entity.
Your NewsItem.php file should look like this:
namespace Your\Bundle\Entity;
use Doctrine\ORM\Mapping as ORM;
use Doctrine\ORM\Mapping\JoinColumn;
/**
* @ORM\Table(name="news_item")
* @ORM\Entity
*/
class NewsItem {
/**
* @var integer
*
* @ORM\Column(name="id", type="integer")
* @ORM\Id
* @ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* @var Category
*
* @ORM\ManyToOne(targetEntity="Category", inversedBy="news_items")
* @ORM\JoinColumn(name="category_id", referencedColumnName="id")
*/
private $category;
// Rest of code omitted.
}
And your Category.php should look like this:
namespace Your\Bundle\Entity;
/**
* @ORM\Table(name="category")
* @ORM\Entity
*/
class Category {
/**
* @var integer
*
* @ORM\Column(name="id", type="integer")
* @ORM\Id
* @ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* @var ArrayCollection
*
* @ORM\OneToMany(targetEntity="NewsItem", mappedBy="category")
*/
private $news_items;
public function __construct(){
$this->news_items = new ArrayCollection();
}
// Rest of code omitted.
}