How to Use the Serializer

How to Use the Serializer

How to Use the Serializer

Symfony provides a serializer to serialize/deserialize to and from objects and different formats (e.g. JSON or XML). Before using it, read the Serializer component docs to get familiar with its philosophy and the normalizers and encoders terminology.

Installation

In applications using Symfony Flex, run this command to install the serializer Symfony pack before using it:

$ composer require symfony/serializer-pack

Using the Serializer Service

Once enabled, the serializer service can be injected in any service where you need it or it can be used in a controller:

// src/Controller/DefaultController.php
namespace App\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Serializer\SerializerInterface;
class DefaultController extends AbstractController
{
    public function index(SerializerInterface $serializer)
    {
        // keep reading for usage examples
    }
}

Or you can use the serialize Twig filter in a template:

{{ object|serialize(format = 'json') }}

See the twig reference for more information.

New in version 5.3: A serialize filter was introduced in Symfony 5.3 that uses the Serializer component.

Adding Normalizers and Encoders

Once enabled, the serializer service will be available in the container. It comes with a set of useful encoders and normalizers.

Encoders supporting the following formats are enabled:

JSON: Symfony\Component\Serializer\Encoder\JsonEncoder
XML: Symfony\Component\Serializer\Encoder\XmlEncoder
CSV: Symfony\Component\Serializer\Encoder\CsvEncoder
YAML: Symfony\Component\Serializer\Encoder\YamlEncoder

As well as the following normalizers:

Symfony\Component\Serializer\Normalizer\ObjectNormalizer to handle typical data objects
Symfony\Component\Serializer\Normalizer\DateTimeNormalizer for objects implementing the DateTimeInterface interface
Symfony\Component\Serializer\Normalizer\DateTimeZoneNormalizer for DateTimeZone objects
Symfony\Component\Serializer\Normalizer\DateIntervalNormalizer for DateInterval objects
Symfony\Component\Serializer\Normalizer\DataUriNormalizer to transform SplFileInfo objects in Data URIs
Symfony\Component\Serializer\Normalizer\FormErrorNormalizer for objects implementing the Symfony\Component\Form\FormInterface to normalize form errors.
Symfony\Component\Serializer\Normalizer\JsonSerializableNormalizer to deal with objects implementing the JsonSerializable interface
Symfony\Component\Serializer\Normalizer\ArrayDenormalizer to denormalize arrays of objects using a notation like MyObject[] (note the []` suffix)
Symfony\Component\Serializer\Normalizer\ConstraintViolationListNormalizer for objects implementing the Symfony\Component\Validator\ConstraintViolationListInterface interface
Symfony\Component\Serializer\Normalizer\ProblemNormalizer for Symfony\Component\ErrorHandler\Exception\FlattenException objects

Custom normalizers and/or encoders can also be loaded by tagging them as serializer.normalizer and serializer.encoder. It’s also possible to set the priority of the tag in order to decide the matching order.

Caution

Always make sure to load the DateTimeNormalizer when serializing the DateTime or DateTimeImmutable classes to avoid excessive memory usage and exposing internal details.

Here is an example on how to load the Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer, a faster alternative to the ObjectNormalizer when data objects always use getters (getXxx()), issers (isXxx()) or hassers (hasXxx()) to read properties and setters (setXxx()) to change properties:

YAML

# config/services.yaml
services:
    get_set_method_normalizer:
        class: Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer
        tags: [serializer.normalizer]

XML

<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        https://symfony.com/schema/dic/services/services-1.0.xsd">
    <services>
        <service id="get_set_method_normalizer" class="Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer">
            <tag name="serializer.normalizer"/>
        </service>
    </services>
</container>

PHP

// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
return function(ContainerConfigurator $configurator) {
    $services = $configurator->services();
    $services->set('get_set_method_normalizer', GetSetMethodNormalizer::class)
        ->tag('serializer.normalizer')
    ;
};

Using Serialization Groups Annotations

To use annotations, first add support for them via the SensioFrameworkExtraBundle:

$ composer require sensio/framework-extra-bundle

Next, add the @Groups annotations to your class:

// src/Entity/Product.php
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Serializer\Annotation\Groups;
/**
 * @ORM\Entity()
 */
class Product
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     * @Groups({"show_product", "list_product"})
     */
    private $id;
    /**
     * @ORM\Column(type="string", length=255)
     * @Groups({"show_product", "list_product"})
     */
    private $name;
    /**
     * @ORM\Column(type="integer")
     * @Groups({"show_product"})
     */
    private $description;
}

You can now choose which groups to use when serializing:

$json = $serializer->serialize(
    $product,
    'json',
    ['groups' => 'show_product']
);

Tip

The value of the groups key can be a single string, or an array of strings.

In addition to the @Groups annotation, the Serializer component also supports YAML or XML files. These files are automatically loaded when being stored in one of the following locations:

All *.yaml and *.xml files in the config/serializer/ directory.
The serialization.yaml or serialization.xml file in the Resources/config/ directory of a bundle;
All *.yaml and *.xml files in the Resources/config/serialization/ directory of a bundle.

Configuring the Metadata Cache

The metadata for the serializer is automatically cached to enhance application performance. By default, the serializer uses the cache.system cache pool which is configured using the cache.system option.

Enabling a Name Converter

The use of a name converter service can be defined in the configuration using the name_converter option.

The built-in CamelCase to snake_case name converter can be enabled by using the serializer.name_converter.camel_case_to_snake_case value:

YAML

# config/packages/framework.yaml
framework:
    # ...
    serializer:
        name_converter: 'serializer.name_converter.camel_case_to_snake_case'

XML

<!-- config/packages/framework.xml -->
<framework:config>
    <!-- ... -->
    <framework:serializer name-converter="serializer.name_converter.camel_case_to_snake_case"/>
</framework:config>

PHP

// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework) {
    $framework->serializer()->nameConverter('serializer.name_converter.camel_case_to_snake_case');
};

Going Further with the Serializer

API Platform provides an API system supporting the following formats:

JSON-LD along with the Hydra Core Vocabulary
OpenAPI v2 (formerly Swagger) and v3
GraphQL
JSON:API
HAL
JSON
XML
YAML
CSV

It is built on top of the Symfony Framework and its Serializer component. It provides custom normalizers and a custom encoder, custom metadata and a caching system.

If you want to leverage the full power of the Symfony Serializer component, take a look at how this bundle works.

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