doctrine2 OneToMany relationship inserts NULL as the foreign key

I have a bi-directional OneToMany relationship using Doctrine 2 as an ORM within the ZendFramework 1.11.2.

Note: Doctrine did not create the database tables. The database is MySQL.

For some reason, when I persist and flush a new link entity to the link table (see below) the foreign key field (container_id) gets set to NULL. However, if the '@' symbol is removed from the 'ManyToOne(targetEntity="Shepherd\Navigation\Domain\Container\Model", inversedBy="links")' line, the foreign key field is populated properly.

Since the entity is added properly to the database when the '@' symbol is removed, there is something wrong with the OneToMany relationship somewhere.

For example, if I have a link model named $link (see pseudo-code below)...

 $link (Shepherd\Navigation\Domain\Link\Model) 
    {
        id:   ''      // auto generated value
        cid:  23      // the foreign key value
        label: test   
        uri: test.com 
        ...           // other values not listed here for brevity
    }

...when the new link model is persisted and the entity manager is flushed, the container_id (foreign key) value from the newly inserted row in the link (shepherd_navigation_link) table is NULL.

    $em // Assume $em is the Entity Manager
    $em->persist($link);
    $em->flush();

    // The container_id in the newly added row in the 
    // link table (shepherd_navigation_link) is NULL 

The link table schema:

CREATE TABLE `shepherd_navigation_link` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `container_id` int(10) unsigned DEFAULT NULL,
  `node_id` int(10) unsigned DEFAULT NULL,
  `parent_id` int(10) unsigned DEFA开发者_如何学编程ULT NULL,
  `label` varchar(100) NOT NULL,
  `options` text,
  `events` text,
  `privilege` varchar(100) NOT NULL,
  `resource` varchar(100) DEFAULT NULL,
  `uri` varchar(300) NOT NULL,
  `visible` int(10) unsigned DEFAULT '1',
  PRIMARY KEY (`id`),
  KEY `container_id` (`container_id`)
) ENGINE=InnoDB
ALTER TABLE `shepherd_navigation_link` ADD FOREIGN KEY (container_id) REFERENCES shepherd_navigation_container(id)

Link entity model:

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

    /** 
     * @Column(name="container_id", type="integer", nullable=false)
     */
     protected $cid;

    /** 
     * @Column(name="node_id", type="integer")
     */
    protected $nid;

    /** 
     * @Column(name="parent_id", type="integer", nullable=false)
     */
    protected $pid;

    /** 
     * @Column
     */
    protected $label;

    /** 
     * @Column(nullable=true)
     */
    protected $options;

    /** 
     * @Column(nullable=true)
     */
    protected $events;

    /** 
     * @Column
     */
    protected $privilege;

    /** 
     * @Column(nullable=true)
     */
    protected $resource;

    /** 
     * @Column
     */
    protected $uri;

    /** 
     * @Column(type="integer", nullable=true)
     */
    protected $visible;

    /**
     * @OneToMany(targetEntity="Model", mappedBy="parent")
     */
    private $children;

    /**
     * @ManyToOne(targetEntity="Model", inversedBy="children")
     */
    private $parent;

    /**
     *) @ManyToOne(targetEntity="Shepherd\Navigation\Domain\Container\Model", inversedBy="links"
     */
    private $container;

    /**
     * @OneToOne(targetEntity="Shepherd\Navigation\Domain\Link\Position", inversedBy="link")
     */
    private $node;

    public function __construct()
    {
        $this->children = new \Doctrine\Common\Collections\ArrayCollection();   
    }

    /** Accessors and Mutators excluded for brevity **/
}

Note: the protected property $cid maps to the container_id column above.

The container table schema:

CREATE TABLE `shepherd_navigation_container` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL,
  `description` text,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB

The container entity model:

/**
 * @Entity
 * @Table(name="shepherd_navigation_container")
 */
class Model
{
    /** 
     * @Id 
     * @Column(type="integer")
     * @GeneratedValue 
     */
    protected $id;

    /** 
     * @Column
     */
    protected $name;

    /** 
     * @Column(nullable=true)
     */
    protected $description;

    /**
     * @OneToMany(targetEntity="Shepherd\Navigation\Domain\Link\Model", mappedBy="container")
     */
    private $links;

    /**
     * Constructor
     */
    public function __construct()
    {
        $this->links = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /** Accessors and Mutators excluded for brevity **/
}

What am I missing? What am I doing wrong?

I figured out the problem (by reading the documentation http://www.doctrine-project.org/docs/orm/2.0/en/tutorials/getting-started-xml-edition.html). It turns out there were actually a few problems.

Problem 1 => I did not provide a method to set the container variable.

// Inside the Link Entity class...

public function setContainer($container)
{
    $this->container = $container;
}

Problem 2 => I did not set the container value. In error, I thought Doctrine 2 did this internally, but I found out the container variable needs to be set prior to flushing.

Foolish oversight on my part.

$link = new Link();
$link->setContainer($container);

// $em is the Entity Manager
$em->persist($link);
$em->flush();

Problem 3 => The container ($container) needed to either be persisted prior to flushing or the @OneToMany definition on the container entity needed to change. I chose to update the container entity definition. Take a look here (http://www.doctrine-project.org/docs/orm/2.0/en/reference/working-with-associations.html#transitive-persistence-cascade-operations) for more information.

// Inside the Container Entity class...
/**
 * @OneToMany(targetEntity="Shepherd\Navigation\Domain\Link\Model", mappedBy="container", cascade={"persist"})
 */

After making these changes and removing the @OneToOne node relationship in the link entity class (turns out I didn't need it), everything worked fine. I hope this helps someone.