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Databases and the Doctrine ORM

Databases and the Doctrine ORM

Symfony doesn't provide a component to work with the database, but it does provide tight integration with a third-party library called Doctrine.

Note

This article is all about using the Doctrine ORM. If you prefer to use raw database queries, see the "How to Use Doctrine DBAL" article instead.

You can also persist data to MongoDB using Doctrine ODM library. See the "DoctrineMongoDBBundle" documentation.

Installing Doctrine

First, install Doctrine, as well as the MakerBundle, which will help generate some code:

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composer require doctrine maker

Configuring the Database

The database connection information is stored as an environment variable called DATABASE_URL. For development, you can find and customize this inside .env:

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# .env

# customize this line!
DATABASE_URL="mysql://db_user:db_password@127.0.0.1:3306/db_name"

# to use sqlite:
# DATABASE_URL="sqlite:///%kernel.project_dir%/var/app.db"

Now that your connection parameters are setup, Doctrine can create the db_name database for you:

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$ php bin/console doctrine:database:create

There are more options in config/packages/doctrine.yaml that you can configure, including your server_version (e.g. 5.7 if you're using MySQL 5.7), which may affect how Doctrine functions.

Tip

There are many other Doctrine commands. Run php bin/console list doctrine to see a full list.

Creating an Entity Class

Suppose you're building an application where products need to be displayed. Without even thinking about Doctrine or databases, you already know that you need a Product object to represent those products. Use the make:entity command to create this class for you:

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$ php bin/console make:entity Product

You now have a new src/Entity/Product.php file:

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// src/Entity/Product.php
namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass="App\Repository\ProductRepository")
 */
class Product
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    // add your own fields
}

This class is called an "entity". And soon, you will be able to save and query Product objects to a product table in your database.

Mapping More Fields / Columns

Each property in the Product entity can be mapped to a column in the product table. By adding some mapping configuration, Doctrine will be able to save a Product object to the product table and query from the product table and turn that data into Product objects:

_images/mapping_single_entity.png

Let's give the Product entity class three more properties and map them to columns in the database. This is usually done with annotations:

  • Annotations
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    // src/Entity/Product.php
    // ...
    
    // this use statement is needed for the annotations
    use Doctrine\ORM\Mapping as ORM;
    
    class Product
    {
        /**
         * @ORM\Id
         * @ORM\GeneratedValue
         * @ORM\Column(type="integer")
         */
        private $id;
    
        /**
         * @ORM\Column(type="string", length=100)
         */
        private $name;
    
        /**
         * @ORM\Column(type="decimal", scale=2, nullable=true)
         */
        private $price;
    }
    
  • YAML
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    # config/doctrine/Product.orm.yml
    App\Entity\Product:
        type: entity
        id:
            id:
                type: integer
                generator: { strategy: AUTO }
        fields:
            name:
                type: string
                length: 100
            price:
                type: decimal
                scale: 2
                nullable: true
    
  • XML
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    <!-- config/doctrine/Product.orm.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
            http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
    
        <entity name="App\Entity\Product">
            <id name="id" type="integer">
                <generator strategy="AUTO" />
            </id>
            <field name="name" type="string" length="100" />
            <field name="price" type="decimal" scale="2" nullable="true" />
        </entity>
    </doctrine-mapping>
    

Doctrine supports a wide variety of different field types, each with their own options. To see a full list of types and options, see Doctrine's Mapping Types documentation. If you want to use XML instead of annotations, add type: xml and dir: '%kernel.project_dir%/config/doctrine to the entity mappings in your config/packages/doctrine.yaml file.

Caution

Be careful not to use reserved SQL keywords as your table or column names (e.g. GROUP or USER). See Doctrine's Reserved SQL keywords documentation for details on how to escape these. Or, configure the table name with @ORM\Table(name="groups") above the class or configure the column name with the name="group_name" option.

Migrations: Creating the Database Tables/Schema

The Product class is fully-configured and ready to save to a product table. Of course, your database doesn't actually have the product table yet. To add the table, you can leverage the DoctrineMigrationsBundle, which is already installed:

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$ php bin/console doctrine:migrations:diff

If everything worked, you should see something like this:

Generated new migration class to "/path/to/project/doctrine/src/Migrations/Version20171122151511.php" from schema differences.

If you open this file, it contains the SQL needed to update your database! To run that SQL, execute your migrations:

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$ php bin/console doctrine:migrations:migrate

This command executes all migration files that have not already been run against your database.

Migrations & Adding more Fields

But what if you need to add a new field property to Product, like a description?

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// src/Entity/Product.php
// ...

class Product
{
    // ...

+     /**
+      * @ORM\Column(type="text")
+      */
+     private $description;
}

The new property is mapped, but it doesn't exist yet in the product table. No problem! Just generate a new migration:

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$ php bin/console doctrine:migrations:diff

This time, the SQL in the generated file will look like this:

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ALTER TABLE product ADD description LONGTEXT NOT NULL

The migration system is smart. It compares all of your entities with the current state of the database and generates the SQL needed to synchronize them! Just like before, execute your migrations:

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$ php bin/console doctrine:migrations:migrate

This will only execute the one new migration file, because DoctrineMigrationsBundle knows that the first migration was already executed earlier. Behind the scenes, it automatically manages a migration_versions table to track this.

Each time you make a change to your schema, run these two commands to generate the migration and then execute it. Be sure to commit the migration files and run execute them when you deploy.

Generating Getters and Setters

Doctrine now knows how to persist a Product object to the database. But the class itself isn't useful yet. All of the properties are private, so there's no way to set data on them!

For that reason, you should create public getters and setters for all the fields you need to modify from outside of the class. If you use an IDE like PhpStorm, it can generate these for you. In PhpStorm, put your cursor anywhere in the class, then go to the Code -> Generate menu and select "Getters and Setters":

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// src/Entity/Product
// ...

class Product
{
    // all of your properties

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

    public function getName()
    {
        return $this->name;
    }

    public function setName($name)
    {
        $this->name = $name;
    }

    // ... getters & setters for price & description
}

Tip

Typically you won't need a setId() method: Doctrine will set this for you automatically.

Persisting Objects to the Database

It's time to save a Product object to the database! Let's create a new controller to experiment:

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$ php bin/console make:controller ProductController

Inside the controller, you can create a new Product object, set data on it, and save it!

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// src/Controller/ProductController.php

namespace App\Controller;

// ...
use App\Entity\Product;

class ProductController extends Controller
{
    /**
     * @Route("/product", name="product")
     */
    public function index()
    {
        // you can fetch the EntityManager via $this->getDoctrine()
        // or you can add an argument to your action: index(EntityManagerInterface $em)
        $em = $this->getDoctrine()->getManager();

        $product = new Product();
        $product->setName('Keyboard');
        $product->setPrice(19.99);
        $product->setDescription('Ergonomic and stylish!');

        // tell Doctrine you want to (eventually) save the Product (no queries yet)
        $em->persist($product);

        // actually executes the queries (i.e. the INSERT query)
        $em->flush();

        return new Response('Saved new product with id '.$product->getId());
    }
}

Try it out!

Congratulations! You just created your first row in the product table. To prove it, you can query the database directly:

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$ php bin/console doctrine:query:sql 'SELECT * FROM product'

Take a look at the previous example in more detail:

  • line 17 The $this->getDoctrine()->getManager() method gets Doctrine's entity manager object, which is the most important object in Doctrine. It's responsible for saving objects to, and fetching objects from, the database.
  • lines 19-22 In this section, you instantiate and work with the $product object like any other normal PHP object.
  • line 25 The persist($product) call tells Doctrine to "manage" the $product object. This does not cause a query to be made to the database.
  • line 28 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 the database. In this example, the $product object's data doesn't exist in the database, so the entity manager executes an INSERT query, creating a new row in the product table.

Note

If the flush() call fails, a Doctrine\ORM\ORMException exception is thrown. See Transactions and Concurrency.

Whether you're creating or updating objects, the workflow is always the same: Doctrine is smart enough to know if it should INSERT of UPDATE your entity.

Fetching Objects from the Database

Fetching an object back out of the database is even easier. Suppose you want to be able to go to /product/1 to see your new product:

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// src/Controller/ProductController.php
// ...

/**
 * @Route("/product/{id}", name="product_show")
 */
public function showAction($id)
{
    $product = $this->getDoctrine()
        ->getRepository(Product::class)
        ->find($id);

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

    return new Response('Check out this great product: '.$product->getName());

    // or render a template
    // in the template, print things with {{ product.name }}
    // return $this->render('product/show.html.twig', ['product' => $product]);
}

Try it out!

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 entities of a certain class.

Once you have a repository object, you have many helper methods:

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$repository = $this->getDoctrine()->getRepository(Product::class);

// query for a single Product by its primary key (usually "id")
$product = $repository->find($id);

// query for a single Product by name
$product = $repository->findOneBy(['name' => 'Keyboard']);
// or find by name and price
$product = $repository->findOneBy([
    'name' => 'Keyboard',
    'price' => 19.99,
]);

// query for multiple Product objects matching the name, ordered by price
$products = $repository->findBy(
    ['name' => 'Keyboard'],
    ['price' => 'ASC']
);

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

You can also add custom methods for more complex queries! More on that later in the Querying for Objects: The Repository section.

Tip

When rendering an HTML page, the web debug toolbar at the bottom of the page will display the number of queries and the time it took to execute them:

_images/doctrine_web_debug_toolbar.png

If the number of database queries is too high, the icon will turn yellow to indicate that something may not be correct. Click on the icon to open the Symfony Profiler and see the exact queries that were executed. If you don't see the web debug toolbar, try running composer require profiler to install it.

Automatically Fetching Objects (ParamConverter)

In many cases, you can use the SensioFrameworkExtraBundle to do the query for you automatically! First, install the bundle in case you don't have it:

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$ composer require annotations

Now, simplify your controller:

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// src/Controller/ProductController.php

use App\Entity\Product;
// ...

/**
 * @Route("/product/{id}", name="product_show")
 */
public function showAction(Product $product)
{
    // use the Product!
    // ...
}

That's it! The bundle uses the {id} from the route to query for the Product by the id column. If it's not found, a 404 page is generated.

There are many more options you can use. Read more about the ParamConverter.

Updating an Object

Once you've fetched an object from Doctrine, updating it is easy:

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/**
 * @Route("/product/edit/{id}")
 */
public function updateAction($id)
{
    $em = $this->getDoctrine()->getManager();
    $product = $em->getRepository(Product::class)->find($id);

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

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

    return $this->redirectToRoute('product_show', [
        'id' => $product->getId()
    ]);
}

Updating an object involves just three steps:

  1. fetching the object from Doctrine;
  2. modifying the object;
  3. calling flush() on the entity manager.

You can call $em->persist($product), but it isn't necessary: Doctrine is already "watching" your object for changes.

Deleting an Object

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

$em->remove($product);
$em->flush();

As you might expect, the remove() method notifies Doctrine that you'd like to remove the given object from the database. The DELETE query isn't actually executed until the flush() method is called.

Querying for Objects: The Repository

You've already seen how the repository object allows you to run basic queries without any work:

// from inside a controller
$repository = $this->getDoctrine()->getRepository(Product::class);

$product = $repository->find($id);

But what if you need a more complex query? When you generated your entity with make:entity, the command also generated a ProductRepository class:

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// src/Repository/ProductRepository.php
namespace App\Repository;

use App\Entity\Product;
use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;

class ProductRepository extends ServiceEntityRepository
{
    public function __construct(RegistryInterface $registry)
    {
        parent::__construct($registry, Product::class);
    }
}

When you fetch your repository (i.e. ->getRepository(Product::class)), it is actually an instance of this object! This is because of the repositoryClass config that was generated at the top of your Product entity class.

Suppose you want to query for all Product objects greater than a certain price. Add a new method for this to your repository:

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// src/Repository/ProductRepository.php

// ...
class ProductRepository extends ServiceEntityRepository
{
    public function __construct(RegistryInterface $registry)
    {
        parent::__construct($registry, Product::class);
    }

    /**
     * @param $price
     * @return Product[]
     */
    public function findAllGreaterThanPrice($price): array
    {
        // automatically knows to selects Products
        // the "p" is an alias you'll use in the rest of the query
        $qb = $this->createQueryBuilder('p')
            ->andWhere('p.price > :price')
            ->setParameter('price', $price)
            ->orderBy('p.price', 'ASC')
            ->getQuery();

        return $qb->execute();

        // to get just one result:
        // $product = $query->setMaxResults(1)->getOneOrNullResult();
    }
}

This uses Doctrine's Query Builder: a very powerful and user-friendly way to write custom queries. Now, you can call this method on the repository:

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// from inside a controller
$minPrice = 10;

$products = $this->getDoctrine()
    ->getRepository(Product::class)
    ->findAllGreaterThanPrice($minPrice);

// ...

If you're in a Injecting Services/Config into a Service, you can type-hint the ProductRepository class and inject it like normal.

For more details, see the Query Builder Documentation from Doctrine.

Querying with DQL or SQL

In addition to the query builder, you can also query with Doctrine Query Language:

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// src/Repository/ProductRepository.php
// ...

public function findAllGreaterThanPrice($price): array
{
    $query = $em->createQuery(
        'SELECT p
        FROM App\Entity\Product p
        WHERE p.price > :price
        ORDER BY p.price ASC'
    )->setParameter('price', 10);

    // returns an array of Product objects
    return $query->execute();
}

Or directly with SQL if you need to:

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// src/Repository/ProductRepository.php
// ...

public function findAllGreaterThanPrice($price): array
{
    $conn = $this->getEntityManager()->getConnection();

    $sql = '
        SELECT * FROM product p
        WHERE p.price > :price
        ORDER BY p.price ASC
        ';
    $stmt = $conn->prepare($sql);
    $stmt->execute(['price' => 10]);

    // returns an array of arrays (i.e. a raw data set)
    return $stmt->fetchAll();
}

With SQL, you will get back raw data, not objects (unless you use the NativeQuery functionality).

Configuration

See the Doctrine config reference.

Relationships and Associations

Doctrine provides all the functionality you need to manage database relationships (also known as associations), including ManyToOne, OneToMany, OneToOne and ManyToMany relationships.

For info, see How to Work with Doctrine Associations / Relations.

Dummy Data Fixtures

Doctrine provides a library that allows you to programmatically load testing data into your project (i.e. "fixture data"). For information, see the "DoctrineFixturesBundle" documentation.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.