Doctrine Parent Child查找无效的Foreach

I am just trying to set up a simple parent-child relationship with Doctrine 2 but I am obviously doing something wrong. I am following what it says on the Association Mapping page of the Doctrine website.

I am getting the following errors:

Warning: Invalid argument supplied for foreach() in .../Doctrine/ORM/Persisters/BasicEntityPersister.php on line 1579

Fatal error: Call to a member function setValue() on a non-object in .../Doctrine/ORM/PersistentCollection.php on line 175

Here is my database setup:

CREATE TABLE IF NOT EXISTS `foo` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `parent_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

Here is my class:

namespace Classes;

/** @Entity @Table(name="foo") */
class Foo
{
    /**
     * @Id @Column(type="integer")
     * @GeneratedValue(strategy="AUTO")
     */
    protected $id;

     /**
     * @OneToMany(targetEntity="classes\Foo", mappedBy="parent_id")
     **/
    private $children;

    /** @ManyToOne(targetEntity="classes\Foo", inversedBy="children") 
     *  @JoinColumn(name="parent_id", referencedColumnName="id")
     **/
    private $parent;


    public function __get($name)
    {
        if(property_exists($this, $name)){
            return $this->$name;
        } else {
            throw new \Exception('Field "' . $name . '" does not exist.');
        }
    }
}

and here is the page that calls it:

$server = '/Applications/XAMPP/htdocs/projects/Scratch';

require_once $server . '/Model/bootstrap.php';

$myFoo = $em->find('classes\Foo',37);

echo $myFoo->id . '<br />';

echo count($myFoo->children);

I can't seem to find this myself, but are namespaces in PHP case sensitive?

The other thing that I've seen used when setting up these kinds of relations is the instantiation of a collection in the entity constructor. This would apply specifically to the children property.

Hope this helps.

While not an answer, here is a work around...

You can use:

$children = $em->getRepository('classes\Foo')->findby(array('parent_id',parentID);