First steps using the ODM

Creating a Document Class

Suppose you're building an application where products need to be displayed. Without even thinking about Doctrine or MongoDB, you already know that you need a Product object to represent those products. Create this class inside the Document subdirectory of your project's source code:

1
// src/Document/Product.php
namespace App\Document;

class Product
{
    protected $name;

    protected $price;
}
2
3
4
5
6
7
8
9

The class - often called a document, meaning a basic class that holds data - helps fulfill the business requirement of needing products in your application. This class can't be persisted to Doctrine MongoDB yet - currently it's only a plain PHP class.

Add Mapping Information

Doctrine allows you to work with MongoDB in a much more interesting way than just fetching data back and forth as an array. Instead, Doctrine allows you to persist entire objects to MongoDB and fetch entire objects out of MongoDB. This works by mapping a PHP class and its properties to entries of a MongoDB collection.

For Doctrine to be able to do this, you have to create metadata, or configuration that tells Doctrine exactly how the Product class and its properties should be mapped to MongoDB. This metadata can be specified in a number of different formats including XML or directly inside the Product class via annotations:

Persisting Objects to MongoDB

Now that you have a mapped Product document complete with getter and setter methods, you're ready to persist data to MongoDB. Let's try it from inside a controller. Create new Controller class inside source directory of your project:

1
// src/App/Controller/ProductController.php
use App\Document\Product;
use Doctrine\ODM\MongoDB\DocumentManager;
use Symfony\Component\HttpFoundation\Response;
// ...

public function createAction(DocumentManager $dm)
{
    $product = new Product();
    $product->setName('A Foo Bar');
    $product->setPrice('19.99');

    $dm->persist($product);
    $dm->flush();

    return new Response('Created product id ' . $product->getId());
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

Let's walk through this example:

• lines 9-11 In this section, you instantiate and work with the $product object like you would with any other, normal PHP object;
• line 13 The persist() method tells Doctrine to "manage" the $product object. This does not actually cause a query to be made to MongoDB (yet);
• line 14 When the flush() method is called, Doctrine looks through all of the objects that it's managing to see if they need to be persisted to MongoDB. In this example, the $product object has not been persisted yet, so the document manager makes a query to MongoDB, which adds a new entry.

When creating or updating objects, the workflow is always the same. In the next section, you'll see how Doctrine is smart enough to update entries if they already exist in MongoDB.

Fetching Objects from MongoDB

Fetching an object back out of MongoDB is also possible. For example, suppose that you've configured a route to display a specific Product based on its id value:

1
public function showAction(DocumentManager $dm, $id)
{
    $product = $dm->getRepository(Product::class)->find($id);

    if (! $product) {
        throw $this->createNotFoundException('No product found for id ' . $id);
    }

    // do something, like pass the $product object into a template
}
2
3
4
5
6
7
8
9
10

When you query for a particular type of object, you always use what's known as its repository. You can think of a repository as a PHP class whose only job is to help you fetch objects of a certain class. You can access the repository object for a document class via:

1
$repository = $dm->getRepository(Product::class);

Once you have your repository, you have access to all sorts of helpful methods:

1
// query by the identifier (usually "id")
$product = $repository->find($id);

// find *all* products
$products = $repository->findAll();

// find a group of products based on an arbitrary column value
$products = $repository->findBy(['price' => 19.99]);
2
3
4
5
6
7
8

You can also take advantage of the useful findBy() and findOneBy() methods to easily fetch objects based on multiple conditions:

1
// query for one product matching by name and price
$product = $repository->findOneBy(['name' => 'foo', 'price' => 19.99]);

// query for all products matching the name, ordered by price
$product = $repository->findBy(
    ['name' => 'foo'],
    ['price' => 'ASC']
);
2
3
4
5
6
7
8

Updating an Object

Once you've fetched an object from Doctrine, let's try to update it. Suppose you have a route that maps a product id to an update action in a controller:

1
public function updateAction(DocumentManager $dm, $id)
{
    $product = $dm->getRepository(Product::class)->find($id);

    if (! $product) {
        throw $this->createNotFoundException('No product found for id ' . $id);
    }

    $product->setName('New product name!');

    $dm->flush();

    return $this->redirectToRoute('homepage');
}
2
3
4
5
6
7
8
9
10
11
12
13
14

Updating an object involves three steps:

1. Fetching the object from Doctrine;
2. Modifying the object;
3. Calling flush() on the document manager.

Notice that calling $dm->persist($product) isn't necessary. Recall that this method tells Doctrine to manage or watch the $product object. In this case, since you fetched the $product object from Doctrine, it's already managed.

Deleting an Object

Deleting an object is very similar, but requires a call to the remove() method of the document manager:

1
$dm->remove($product);
$dm->flush();
2

The remove() method notifies Doctrine that you'd like to remove the given document from the MongoDB. The actual delete operation however, isn't executed until the flush() method is called.