Blending the ORM and MongoDB ODM

Define Product

First lets define our `Product` document:

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<?php

namespace Documents;

/** @Document */
class Product
{
    /** @Id */
    private $id;

    /** @Field(type="string") */
    private $title;

    public function getId()
    {
        return $this->id;
    }

    public function getTitle()
    {
        return $this->title;
    }

    public function setTitle($title)
    {
        $this->title = $title;
    }
}
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Define Entity

Next create the `Order` entity that has a `$product` and `$productId` property linking it to the `Product` that is stored with MongoDB:

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<?php

namespace Entities;

use Documents\Product;

/**
 * @Entity
 * @Table(name="orders")
 */
class Order
{
    /**
     * @Id @Column(type="integer")
     * @GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @Column(type="string")
     */
    private $productId;

    /**
     * @var Documents\Product
     */
    private $product;

    public function getId()
    {
        return $this->id;
    }

    public function getProductId()
    {
        return $this->productId;
    }

    public function setProduct(Product $product)
    {
        $this->productId = $product->getId();
        $this->product = $product;
    }

    public function getProduct()
    {
        return $this->product;
    }
}
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Event Subscriber

Now we need to setup an event subscriber that will set the `$product` property of all `Order` instances to a reference to the document product so it can be lazily loaded when it is accessed the first time. So first register a new event subscriber:

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<?php

$eventManager = $em->getEventManager();
$eventManager->addEventListener(
    array(\Doctrine\ORM\Events::postLoad), new MyEventSubscriber($dm)
);
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So now we need to define a class named `MyEventSubscriber` and pass a dependency to the `DocumentManager`. It will have a `postLoad()` method that sets the product document reference:

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<?php

use Doctrine\ODM\MongoDB\DocumentManager;
use Doctrine\ORM\Event\LifecycleEventArgs;

class MyEventSubscriber
{
    public function __construct(DocumentManager $dm)
    {
        $this->dm = $dm;
    }

    public function postLoad(LifecycleEventArgs $eventArgs)
    {
        $order = $eventArgs->getEntity();
        $em = $eventArgs->getEntityManager();
        $productReflProp = $em->getClassMetadata('Entities\Order')
            ->reflClass->getProperty('product');
        $productReflProp->setAccessible(true);
        $productReflProp->setValue(
            $order, $this->dm->getReference('Documents\Product', $order->getProductId())
        );
    }
}
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The `postLoad` method will be invoked after an ORM entity is loaded from the database. This allows us to use the `DocumentManager` to set the `$product` property with a reference to the `Product` document with the product id we previously stored.

Working with Products and Orders

First create a new `Product`:

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<?php

$product = new \Documents\Product();
$product->setTitle('Test Product');
$dm->persist($product);
$dm->flush();
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Now create a new `Order` and link it to a `Product` in MySQL:

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<?php

$order = new \Entities\Order();
$order->setProduct($product);
$em->persist($order);
$em->flush();
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Later we can retrieve the entity and lazily load the reference to the document in MongoDB:

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<?php

$order = $em->find('Order', $order->getId());

// Instance of an uninitialized product proxy
$product = $order->getProduct();

// Initializes proxy and queries the database
echo "Order Title: " . $product->getTitle();
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If you were to print the `$order` you would see that we got back regular PHP objects:

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<?php

print_r($order);
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The above would output the following:

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Order Object
(
    [id:Entities\Order:private] => 53
    [productId:Entities\Order:private] => 4c74a1868ead0ed7a9000000
    [product:Entities\Order:private] => Proxies\DocumentsProductProxy Object
        (
            [__isInitialized__] => 1
            [id:Documents\Product:private] => 4c74a1868ead0ed7a9000000
            [title:Documents\Product:private] => Test Product
        )
)
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