.. index::
   single: Serializer
   single: Components; Serializer

The Serializer Component

The Serializer component is meant to be used to turn objects into a specific format (XML, JSON, YAML, ...) and the other way around.

In order to do so, the Serializer component follows the following schema.

As you can see in the picture above, an array is used as an intermediary between objects and serialized contents. This way, encoders will only deal with turning specific formats into arrays and vice versa. The same way, Normalizers will deal with turning specific objects into arrays and vice versa.

Serialization is a complex topic. This component may not cover all your use cases out of the box, but it can be useful for developing tools to serialize and deserialize your objects.

Installation

$ composer require symfony/serializer

To use the ObjectNormalizer, the :doc:`PropertyAccess component </components/property_access>` must also be installed.

Usage

.. seealso::

    This article explains the philosophy of the Serializer and gets you familiar
    with the concepts of normalizers and encoders. The code examples assume
    that you use the Serializer as an independent component. If you are using
    the Serializer in a Symfony application, read :doc:`/serializer` after you
    finish this article.

To use the Serializer component, set up the :class:`Symfony\\Component\\Serializer\\Serializer` specifying which encoders and normalizer are going to be available:

use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Encoder\XmlEncoder;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$encoders = [new XmlEncoder(), new JsonEncoder()];
$normalizers = [new ObjectNormalizer()];

$serializer = new Serializer($normalizers, $encoders);

The preferred normalizer is the :class:`Symfony\\Component\\Serializer\\Normalizer\\ObjectNormalizer`, but other normalizers are available. All the examples shown below use the ObjectNormalizer.

Serializing an Object

For the sake of this example, assume the following class already exists in your project:

namespace App\Model;

class Person
{
    private $age;
    private $name;
    private $sportsperson;
    private $createdAt;

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

    public function getAge()
    {
        return $this->age;
    }

    public function getCreatedAt()
    {
        return $this->createdAt;
    }

    // Issers
    public function isSportsperson()
    {
        return $this->sportsperson;
    }

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

    public function setAge($age)
    {
        $this->age = $age;
    }

    public function setSportsperson($sportsperson)
    {
        $this->sportsperson = $sportsperson;
    }

    public function setCreatedAt($createdAt)
    {
        $this->createdAt = $createdAt;
    }
}

Now, if you want to serialize this object into JSON, you only need to use the Serializer service created before:

$person = new App\Model\Person();
$person->setName('foo');
$person->setAge(99);
$person->setSportsperson(false);

$jsonContent = $serializer->serialize($person, 'json');

// $jsonContent contains {"name":"foo","age":99,"sportsperson":false,"createdAt":null}

echo $jsonContent; // or return it in a Response

The first parameter of the :method:`Symfony\\Component\\Serializer\\Serializer::serialize` is the object to be serialized and the second is used to choose the proper encoder, in this case :class:`Symfony\\Component\\Serializer\\Encoder\\JsonEncoder`.

Deserializing an Object

You'll now learn how to do the exact opposite. This time, the information of the Person class would be encoded in XML format:

use App\Model\Person;

$data = <<<EOF
<person>
    <name>foo</name>
    <age>99</age>
    <sportsperson>false</sportsperson>
</person>
EOF;

$person = $serializer->deserialize($data, Person::class, 'xml');

In this case, :method:`Symfony\\Component\\Serializer\\Serializer::deserialize` needs three parameters:

The information to be decoded
The name of the class this information will be decoded to
The encoder used to convert that information into an array

By default, additional attributes that are not mapped to the denormalized object will be ignored by the Serializer component. If you prefer to throw an exception when this happens, set the AbstractNormalizer::ALLOW_EXTRA_ATTRIBUTES context option to false and provide an object that implements ClassMetadataFactoryInterface when constructing the normalizer:

$data = <<<EOF
<person>
    <name>foo</name>
    <age>99</age>
    <city>Paris</city>
</person>
EOF;

// $loader is any of the valid loaders explained later in this article
$classMetadataFactory = new ClassMetadataFactory($loader);
$normalizer = new ObjectNormalizer($classMetadataFactory);
$serializer = new Serializer([$normalizer]);

// this will throw a Symfony\Component\Serializer\Exception\ExtraAttributesException
// because "city" is not an attribute of the Person class
$person = $serializer->deserialize($data, 'App\Model\Person', 'xml', [
    AbstractNormalizer::ALLOW_EXTRA_ATTRIBUTES => false,
]);

Deserializing in an Existing Object

The serializer can also be used to update an existing object:

// ...
$person = new Person();
$person->setName('bar');
$person->setAge(99);
$person->setSportsperson(true);

$data = <<<EOF
<person>
    <name>foo</name>
    <age>69</age>
</person>
EOF;

$serializer->deserialize($data, Person::class, 'xml', [AbstractNormalizer::OBJECT_TO_POPULATE => $person]);
// $person = App\Model\Person(name: 'foo', age: '69', sportsperson: true)

This is a common need when working with an ORM.

The AbstractNormalizer::OBJECT_TO_POPULATE is only used for the top level object. If that object is the root of a tree structure, all child elements that exist in the normalized data will be re-created with new instances.

When the AbstractObjectNormalizer::DEEP_OBJECT_TO_POPULATE option is set to true, existing children of the root OBJECT_TO_POPULATE are updated from the normalized data, instead of the denormalizer re-creating them. Note that DEEP_OBJECT_TO_POPULATE only works for single child objects, but not for arrays of objects. Those will still be replaced when present in the normalized data.

Attributes Groups

Sometimes, you want to serialize different sets of attributes from your entities. Groups are a handy way to achieve this need.

Assume you have the following plain-old-PHP object:

namespace Acme;

class MyObj
{
    public $foo;

    private $bar;

    public function getBar()
    {
        return $this->bar;
    }

    public function setBar($bar)
    {
        return $this->bar = $bar;
    }
}

The definition of serialization can be specified using annotations, XML or YAML. The :class:`Symfony\\Component\\Serializer\\Mapping\\Factory\\ClassMetadataFactory` that will be used by the normalizer must be aware of the format to use.

The following code shows how to initialize the :class:`Symfony\\Component\\Serializer\\Mapping\\Factory\\ClassMetadataFactory` for each format:

Annotations in PHP files:

use Doctrine\Common\Annotations\AnnotationReader;
use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;

$classMetadataFactory = new ClassMetadataFactory(new AnnotationLoader(new AnnotationReader()));

YAML files:

use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Symfony\Component\Serializer\Mapping\Loader\YamlFileLoader;

$classMetadataFactory = new ClassMetadataFactory(new YamlFileLoader('/path/to/your/definition.yaml'));

XML files:

use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Symfony\Component\Serializer\Mapping\Loader\XmlFileLoader;

$classMetadataFactory = new ClassMetadataFactory(new XmlFileLoader('/path/to/your/definition.xml'));

Then, create your groups definition:

.. configuration-block::

    .. code-block:: php-annotations

        namespace Acme;

        use Symfony\Component\Serializer\Annotation\Groups;

        class MyObj
        {
            /**
             * @Groups({"group1", "group2"})
             */
            public $foo;

            /**
             * @Groups("group3")
             */
            public function getBar() // is* methods are also supported
            {
                return $this->bar;
            }

            // ...
        }

    .. code-block:: yaml

        Acme\MyObj:
            attributes:
                foo:
                    groups: ['group1', 'group2']
                bar:
                    groups: ['group3']

    .. code-block:: xml

        <?xml version="1.0" ?>
        <serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
                https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
        >
            <class name="Acme\MyObj">
                <attribute name="foo">
                    <group>group1</group>
                    <group>group2</group>
                </attribute>

                <attribute name="bar">
                    <group>group3</group>
                </attribute>
            </class>
        </serializer>

You are now able to serialize only attributes in the groups you want:

use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$obj = new MyObj();
$obj->foo = 'foo';
$obj->setBar('bar');

$normalizer = new ObjectNormalizer($classMetadataFactory);
$serializer = new Serializer([$normalizer]);

$data = $serializer->normalize($obj, null, ['groups' => 'group1']);
// $data = ['foo' => 'foo'];

$obj2 = $serializer->denormalize(
    ['foo' => 'foo', 'bar' => 'bar'],
    'MyObj',
    null,
    ['groups' => ['group1', 'group3']]
);
// $obj2 = MyObj(foo: 'foo', bar: 'bar')

Selecting Specific Attributes

It is also possible to serialize only a set of specific attributes:

use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

class User
{
    public $familyName;
    public $givenName;
    public $company;
}

class Company
{
    public $name;
    public $address;
}

$company = new Company();
$company->name = 'Les-Tilleuls.coop';
$company->address = 'Lille, France';

$user = new User();
$user->familyName = 'Dunglas';
$user->givenName = 'Kévin';
$user->company = $company;

$serializer = new Serializer([new ObjectNormalizer()]);

$data = $serializer->normalize($user, null, [AbstractNormalizer::ATTRIBUTES => ['familyName', 'company' => ['name']]]);
// $data = ['familyName' => 'Dunglas', 'company' => ['name' => 'Les-Tilleuls.coop']];

Only attributes that are not ignored (see below) are available. If some serialization groups are set, only attributes allowed by those groups can be used.

As for groups, attributes can be selected during both the serialization and deserialization process.

Ignoring Attributes

As an option, there's a way to ignore attributes from the origin object. To remove those attributes provide an array via the AbstractNormalizer::IGNORED_ATTRIBUTES key in the context parameter of the desired serializer method:

use Acme\Person;
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$person = new Person();
$person->setName('foo');
$person->setAge(99);

$normalizer = new ObjectNormalizer();
$encoder = new JsonEncoder();

$serializer = new Serializer([$normalizer], [$encoder]);
$serializer->serialize($person, 'json', [AbstractNormalizer::IGNORED_ATTRIBUTES => ['age']]); // Output: {"name":"foo"}

Converting Property Names when Serializing and Deserializing

Sometimes serialized attributes must be named differently than properties or getter/setter methods of PHP classes.

The Serializer component provides a handy way to translate or map PHP field names to serialized names: The Name Converter System.

Given you have the following object:

class Company
{
    public $name;
    public $address;
}

And in the serialized form, all attributes must be prefixed by org_ like the following:

{"org_name": "Acme Inc.", "org_address": "123 Main Street, Big City"}

A custom name converter can handle such cases:

use Symfony\Component\Serializer\NameConverter\NameConverterInterface;

class OrgPrefixNameConverter implements NameConverterInterface
{
    public function normalize($propertyName)
    {
        return 'org_'.$propertyName;
    }

    public function denormalize($propertyName)
    {
        // removes 'org_' prefix
        return 'org_' === substr($propertyName, 0, 4) ? substr($propertyName, 4) : $propertyName;
    }
}

The custom name converter can be used by passing it as second parameter of any class extending :class:`Symfony\\Component\\Serializer\\Normalizer\\AbstractNormalizer`, including :class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer` and :class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`:

use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$nameConverter = new OrgPrefixNameConverter();
$normalizer = new ObjectNormalizer(null, $nameConverter);

$serializer = new Serializer([$normalizer], [new JsonEncoder()]);

$company = new Company();
$company->name = 'Acme Inc.';
$company->address = '123 Main Street, Big City';

$json = $serializer->serialize($company, 'json');
// {"org_name": "Acme Inc.", "org_address": "123 Main Street, Big City"}
$companyCopy = $serializer->deserialize($json, Company::class, 'json');
// Same data as $company

Note

You can also implement :class:`Symfony\\Component\\Serializer\\NameConverter\\AdvancedNameConverterInterface` to access to the current class name, format and context.

CamelCase to snake_case

In many formats, it's common to use underscores to separate words (also known as snake_case). However, in Symfony applications is common to use CamelCase to name properties (even though the PSR-1 standard doesn't recommend any specific case for property names).

Symfony provides a built-in name converter designed to transform between snake_case and CamelCased styles during serialization and deserialization processes:

use Symfony\Component\Serializer\NameConverter\CamelCaseToSnakeCaseNameConverter;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;

$normalizer = new ObjectNormalizer(null, new CamelCaseToSnakeCaseNameConverter());

class Person
{
    private $firstName;

    public function __construct($firstName)
    {
        $this->firstName = $firstName;
    }

    public function getFirstName()
    {
        return $this->firstName;
    }
}

$kevin = new Person('Kévin');
$normalizer->normalize($kevin);
// ['first_name' => 'Kévin'];

$anne = $normalizer->denormalize(['first_name' => 'Anne'], 'Person');
// Person object with firstName: 'Anne'

Configure name conversion using metadata

When using this component inside a Symfony application and the class metadata factory is enabled as explained in the :ref:`Attributes Groups section <component-serializer-attributes-groups>`, this is already set up and you only need to provide the configuration. Otherwise:

// ...
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\NameConverter\MetadataAwareNameConverter;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$classMetadataFactory = new ClassMetadataFactory(new AnnotationLoader(new AnnotationReader()));

$metadataAwareNameConverter = new MetadataAwareNameConverter($classMetadataFactory);

$serializer = new Serializer(
    [new ObjectNormalizer($classMetadataFactory, $metadataAwareNameConverter)],
    ['json' => new JsonEncoder()]
);

Now configure your name conversion mapping. Consider an application that defines a Person entity with a firstName property:

.. configuration-block::

    .. code-block:: php-annotations

        namespace App\Entity;

        use Symfony\Component\Serializer\Annotation\SerializedName;

        class Person
        {
            /**
             * @SerializedName("customer_name")
             */
            private $firstName;

            public function __construct($firstName)
            {
                $this->firstName = $firstName;
            }

            // ...
        }

    .. code-block:: yaml

        App\Entity\Person:
            attributes:
                firstName:
                    serialized_name: customer_name

    .. code-block:: xml

        <?xml version="1.0" ?>
        <serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
                https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
        >
            <class name="App\Entity\Person">
                <attribute name="firstName" serialized-name="customer_name"/>
            </class>
        </serializer>

This custom mapping is used to convert property names when serializing and deserializing objects:

$serialized = $serializer->serialize(new Person("Kévin"));
// {"customer_name": "Kévin"}

Serializing Boolean Attributes

If you are using isser methods (methods prefixed by is, like App\Model\Person::isSportsperson()), the Serializer component will automatically detect and use it to serialize related attributes.

The ObjectNormalizer also takes care of methods starting with has, add and remove.

Using Callbacks to Serialize Properties with Object Instances

When serializing, you can set a callback to format a specific object property:

use App\Model\Person;
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
use Symfony\Component\Serializer\Serializer;

$encoder = new JsonEncoder();

// all callback parameters are optional (you can omit the ones you don't use)
$dateCallback = function ($innerObject, $outerObject, string $attributeName, string $format = null, array $context = []) {
    return $innerObject instanceof \DateTime ? $innerObject->format(\DateTime::ISO8601) : '';
};

$defaultContext = [
    AbstractNormalizer::CALLBACKS => [
        'createdAt' => $dateCallback,
    ],
];

$normalizer = new GetSetMethodNormalizer(null, null, null, null, null, $defaultContext);

$serializer = new Serializer([$normalizer], [$encoder]);

$person = new Person();
$person->setName('cordoval');
$person->setAge(34);
$person->setCreatedAt(new \DateTime('now'));

$serializer->serialize($person, 'json');
// Output: {"name":"cordoval", "age": 34, "createdAt": "2014-03-22T09:43:12-0500"}

Normalizers

There are several types of normalizers available:

:class:`Symfony\\Component\\Serializer\\Normalizer\\ObjectNormalizer`

This normalizer leverages the :doc:`PropertyAccess Component </components/property_access>` to read and write in the object. It means that it can access to properties directly and through getters, setters, hassers, adders and removers. It supports calling the constructor during the denormalization process.

Objects are normalized to a map of property names and values (names are generated removing the get, set, has, is or remove prefix from the method name and transforming the first letter to lowercase; e.g. getFirstName() -> firstName).

The ObjectNormalizer is the most powerful normalizer. It is configured by default in Symfony applications with the Serializer component enabled.

:class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer`

This normalizer reads the content of the class by calling the "getters" (public methods starting with "get"). It will denormalize data by calling the constructor and the "setters" (public methods starting with "set").

Objects are normalized to a map of property names and values (names are generated removing the get prefix from the method name and transforming the first letter to lowercase; e.g. getFirstName() -> firstName).

:class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`

This normalizer directly reads and writes public properties as well as private and protected properties (from both the class and all of its parent classes). It supports calling the constructor during the denormalization process.

Objects are normalized to a map of property names to property values.

:class:`Symfony\\Component\\Serializer\\Normalizer\\JsonSerializableNormalizer`

This normalizer works with classes that implement :phpclass:`JsonSerializable`.

It will call the :phpmethod:`JsonSerializable::jsonSerialize` method and then further normalize the result. This means that nested :phpclass:`JsonSerializable` classes will also be normalized.

This normalizer is particularly helpful when you want to gradually migrate from an existing codebase using simple :phpfunction:`json_encode` to the Symfony Serializer by allowing you to mix which normalizers are used for which classes.

Unlike with :phpfunction:`json_encode` circular references can be handled.

:class:`Symfony\\Component\\Serializer\\Normalizer\\DateTimeNormalizer`

This normalizer converts :phpclass:`DateTimeInterface` objects (e.g. :phpclass:`DateTime` and :phpclass:`DateTimeImmutable`) into strings. By default, it uses the RFC3339 format.

:class:`Symfony\\Component\\Serializer\\Normalizer\\DateTimeZoneNormalizer`

This normalizer converts :phpclass:`DateTimeZone` objects into strings that represent the name of the timezone according to the list of PHP timezones.

:class:`Symfony\\Component\\Serializer\\Normalizer\\DataUriNormalizer`

This normalizer converts :phpclass:`SplFileInfo` objects into a data URI string (data:...) such that files can be embedded into serialized data.

:class:`Symfony\\Component\\Serializer\\Normalizer\\DateIntervalNormalizer`

This normalizer converts :phpclass:`DateInterval` objects into strings. By default, it uses the P%yY%mM%dDT%hH%iM%sS format.

:class:`Symfony\\Component\\Serializer\\Normalizer\\ConstraintViolationListNormalizer`

This normalizer converts objects that implement :class:`Symfony\\Component\\Validator\\ConstraintViolationListInterface` into a list of errors according to the RFC 7807 standard.

Encoders

Encoders turn arrays into formats and vice versa. They implement :class:`Symfony\\Component\\Serializer\\Encoder\\EncoderInterface` for encoding (array to format) and :class:`Symfony\\Component\\Serializer\\Encoder\\DecoderInterface` for decoding (format to array).

You can add new encoders to a Serializer instance by using its second constructor argument:

use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Encoder\XmlEncoder;
use Symfony\Component\Serializer\Serializer;

$encoders = [new XmlEncoder(), new JsonEncoder()];
$serializer = new Serializer([], $encoders);

Built-in Encoders

The Serializer component provides several built-in encoders:

:class:`Symfony\\Component\\Serializer\\Encoder\\JsonEncoder`: This class encodes and decodes data in JSON.
:class:`Symfony\\Component\\Serializer\\Encoder\\XmlEncoder`: This class encodes and decodes data in XML.
:class:`Symfony\\Component\\Serializer\\Encoder\\YamlEncoder`: This encoder encodes and decodes data in YAML. This encoder requires the :doc:`Yaml Component </components/yaml>`.
:class:`Symfony\\Component\\Serializer\\Encoder\\CsvEncoder`: This encoder encodes and decodes data in CSV.

All these encoders are enabled by default when using the Serializer component in a Symfony application.

The `JsonEncoder`

The JsonEncoder encodes to and decodes from JSON strings, based on the PHP :phpfunction:`json_encode` and :phpfunction:`json_decode` functions.

The `CsvEncoder`

The CsvEncoder encodes to and decodes from CSV.

The `XmlEncoder`

This encoder transforms arrays into XML and vice versa.

For example, take an object normalized as following:

['foo' => [1, 2], 'bar' => true];

The XmlEncoder will encode this object like that:

<?xml version="1.0"?>
<response>
    <foo>1</foo>
    <foo>2</foo>
    <bar>1</bar>
</response>

Be aware that this encoder will consider keys beginning with @ as attributes, and will use the key #comment for encoding XML comments:

$encoder = new XmlEncoder();
$encoder->encode([
    'foo' => ['@bar' => 'value'],
    'qux' => ['#comment' => 'A comment'],
], 'xml');
// will return:
// <?xml version="1.0"?>
// <response>
//     <foo bar="value"/>
//     <qux><!-- A comment --!><qux>
// </response>

You can pass the context key as_collection in order to have the results always as a collection.

Tip

XML comments are ignored by default when decoding contents, but this behavior can be changed with the optional $decoderIgnoredNodeTypes argument of the XmlEncoder class constructor.

Data with #comment keys are encoded to XML comments by default. This can be changed with the optional $encoderIgnoredNodeTypes argument of the XmlEncoder class constructor.

The `YamlEncoder`

This encoder requires the :doc:`Yaml Component </components/yaml>` and transforms from and to Yaml.

Skipping `null` Values

By default, the Serializer will preserve properties containing a null value. You can change this behavior by setting the AbstractObjectNormalizer::SKIP_NULL_VALUES context option to true:

$dummy = new class {
    public $foo;
    public $bar = 'notNull';
};

$normalizer = new ObjectNormalizer();
$result = $normalizer->normalize($dummy, 'json', [AbstractObjectNormalizer::SKIP_NULL_VALUES => true]);
// ['bar' => 'notNull']

Handling Circular References

Circular references are common when dealing with entity relations:

class Organization
{
    private $name;
    private $members;

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

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

    public function setMembers(array $members)
    {
        $this->members = $members;
    }

    public function getMembers()
    {
        return $this->members;
    }
}

class Member
{
    private $name;
    private $organization;

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

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

    public function setOrganization(Organization $organization)
    {
        $this->organization = $organization;
    }

    public function getOrganization()
    {
        return $this->organization;
    }
}

To avoid infinite loops, :class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer` or :class:`Symfony\\Component\\Serializer\\Normalizer\\ObjectNormalizer` throw a :class:`Symfony\\Component\\Serializer\\Exception\\CircularReferenceException` when such a case is encountered:

$member = new Member();
$member->setName('Kévin');

$organization = new Organization();
$organization->setName('Les-Tilleuls.coop');
$organization->setMembers([$member]);

$member->setOrganization($organization);

echo $serializer->serialize($organization, 'json'); // Throws a CircularReferenceException

The key circular_reference_limit in the default context sets the number of times it will serialize the same object before considering it a circular reference. The default value is 1.

Instead of throwing an exception, circular references can also be handled by custom callables. This is especially useful when serializing entities having unique identifiers:

$encoder = new JsonEncoder();
$defaultContext = [
    AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER => function ($object, $format, $context) {
        return $object->getName();
    },
];
$normalizer = new ObjectNormalizer(null, null, null, null, null, null, $defaultContext);

$serializer = new Serializer([$normalizer], [$encoder]);
var_dump($serializer->serialize($org, 'json'));
// {"name":"Les-Tilleuls.coop","members":[{"name":"K\u00e9vin", organization: "Les-Tilleuls.coop"}]}

Handling Serialization Depth

The Serializer component is able to detect and limit the serialization depth. It is especially useful when serializing large trees. Assume the following data structure:

namespace Acme;

class MyObj
{
    public $foo;

    /**
     * @var self
     */
    public $child;
}

$level1 = new MyObj();
$level1->foo = 'level1';

$level2 = new MyObj();
$level2->foo = 'level2';
$level1->child = $level2;

$level3 = new MyObj();
$level3->foo = 'level3';
$level2->child = $level3;

The serializer can be configured to set a maximum depth for a given property. Here, we set it to 2 for the $child property:

.. configuration-block::

    .. code-block:: php-annotations

        namespace Acme;

        use Symfony\Component\Serializer\Annotation\MaxDepth;

        class MyObj
        {
            /**
             * @MaxDepth(2)
             */
            public $child;

            // ...
        }

    .. code-block:: yaml

        Acme\MyObj:
            attributes:
                child:
                    max_depth: 2

    .. code-block:: xml

        <?xml version="1.0" ?>
        <serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
                https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
        >
            <class name="Acme\MyObj">
                <attribute name="child" max-depth="2"/>
            </class>
        </serializer>

The metadata loader corresponding to the chosen format must be configured in order to use this feature. It is done automatically when using the Serializer component in a Symfony application. When using the standalone component, refer to :ref:`the groups documentation <component-serializer-attributes-groups>` to learn how to do that.

The check is only done if the AbstractObjectNormalizer::ENABLE_MAX_DEPTH key of the serializer context is set to true. In the following example, the third level is not serialized because it is deeper than the configured maximum depth of 2:

$result = $serializer->normalize($level1, null, [AbstractObjectNormalizer::ENABLE_MAX_DEPTH => true]);
/*
$result = [
    'foo' => 'level1',
    'child' => [
        'foo' => 'level2',
        'child' => [
            'child' => null,
        ],
    ],
];
*/

Instead of throwing an exception, a custom callable can be executed when the maximum depth is reached. This is especially useful when serializing entities having unique identifiers:

use Doctrine\Common\Annotations\AnnotationReader;
use Symfony\Component\Serializer\Annotation\MaxDepth;
use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;
use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

class Foo
{
    public $id;

    /**
     * @MaxDepth(1)
     */
    public $child;
}

$level1 = new Foo();
$level1->id = 1;

$level2 = new Foo();
$level2->id = 2;
$level1->child = $level2;

$level3 = new Foo();
$level3->id = 3;
$level2->child = $level3;

$classMetadataFactory = new ClassMetadataFactory(new AnnotationLoader(new AnnotationReader()));

// all callback parameters are optional (you can omit the ones you don't use)
$maxDepthHandler = function ($innerObject, $outerObject, string $attributeName, string $format = null, array $context = []) {
    return '/foos/'.$innerObject->id;
};

$defaultContext = [
    AbstractObjectNormalizer::MAX_DEPTH_HANDLER => $maxDepthHandler,
];
$normalizer = new ObjectNormalizer($classMetadataFactory, null, null, null, null, null, $defaultContext);

$serializer = new Serializer([$normalizer]);

$result = $serializer->normalize($level1, null, [AbstractObjectNormalizer::ENABLE_MAX_DEPTH => true]);
/*
$result = [
    'id' => 1,
    'child' => [
        'id' => 2,
        'child' => '/foos/3',
    ],
];
*/

Handling Arrays

The Serializer component is capable of handling arrays of objects as well. Serializing arrays works just like serializing a single object:

use Acme\Person;

$person1 = new Person();
$person1->setName('foo');
$person1->setAge(99);
$person1->setSportsman(false);

$person2 = new Person();
$person2->setName('bar');
$person2->setAge(33);
$person2->setSportsman(true);

$persons = [$person1, $person2];
$data = $serializer->serialize($persons, 'json');

// $data contains [{"name":"foo","age":99,"sportsman":false},{"name":"bar","age":33,"sportsman":true}]

If you want to deserialize such a structure, you need to add the :class:`Symfony\\Component\\Serializer\\Normalizer\\ArrayDenormalizer` to the set of normalizers. By appending [] to the type parameter of the :method:`Symfony\\Component\\Serializer\\Serializer::deserialize` method, you indicate that you're expecting an array instead of a single object:

use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\ArrayDenormalizer;
use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
use Symfony\Component\Serializer\Serializer;

$serializer = new Serializer(
    [new GetSetMethodNormalizer(), new ArrayDenormalizer()],
    [new JsonEncoder()]
);

$data = ...; // The serialized data from the previous example
$persons = $serializer->deserialize($data, 'Acme\Person[]', 'json');

The `XmlEncoder`

This encoder transforms arrays into XML and vice versa. For example, take an object normalized as following:

['foo' => [1, 2], 'bar' => true];

The XmlEncoder encodes this object as follows:

<?xml version="1.0"?>
<response>
    <foo>1</foo>
    <foo>2</foo>
    <bar>1</bar>
</response>

The array keys beginning with @ are considered XML attributes:

['foo' => ['@bar' => 'value']];

// is encoded as follows:
// <?xml version="1.0"?>
// <response>
//     <foo bar="value"/>
// </response>

Use the special # key to define the data of a node:

['foo' => ['@bar' => 'value', '#' => 'baz']];

// is encoded as follows:
// <?xml version="1.0"?>
// <response>
//     <foo bar="value">
//        baz
//     </foo>
// </response>

Context

The encode() method defines a third optional parameter called context which defines the configuration options for the XmlEncoder an associative array:

$xmlEncoder->encode($array, 'xml', $context);

These are the options available:

xml_format_output: If set to true, formats the generated XML with line breaks and indentation.
xml_version: Sets the XML version attribute (default: 1.1).
xml_encoding: Sets the XML encoding attribute (default: utf-8).
xml_standalone: Adds standalone attribute in the generated XML (default: true).
xml_root_node_name: Sets the root node name (default: response).
remove_empty_tags: If set to true, removes all empty tags in the generated XML.

Handling Constructor Arguments

If the class constructor defines arguments, as usually happens with Value Objects, the serializer won't be able to create the object if some arguments are missing. In those cases, use the default_constructor_arguments context option:

use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

class MyObj
{
    private $foo;
    private $bar;

    public function __construct($foo, $bar)
    {
        $this->foo = $foo;
        $this->bar = $bar;
    }
}

$normalizer = new ObjectNormalizer($classMetadataFactory);
$serializer = new Serializer([$normalizer]);

$data = $serializer->denormalize(
    ['foo' => 'Hello'],
    'MyObj',
    [AbstractNormalizer::DEFAULT_CONSTRUCTOR_ARGUMENTS => [
        'MyObj' => ['foo' => '', 'bar' => ''],
    ]]
);
// $data = new MyObj('Hello', '');

Recursive Denormalization and Type Safety

The Serializer component can use the :doc:`PropertyInfo Component </components/property_info>` to denormalize complex types (objects). The type of the class' property will be guessed using the provided extractor and used to recursively denormalize the inner data.

When using this component in a Symfony application, all normalizers are automatically configured to use the registered extractors. When using the component standalone, an implementation of :class:`Symfony\\Component\\PropertyInfo\\PropertyTypeExtractorInterface`, (usually an instance of :class:`Symfony\\Component\\PropertyInfo\\PropertyInfoExtractor`) must be passed as the 4th parameter of the ObjectNormalizer:

namespace Acme;

use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

class ObjectOuter
{
    private $inner;
    private $date;

    public function getInner()
    {
        return $this->inner;
    }

    public function setInner(ObjectInner $inner)
    {
        $this->inner = $inner;
    }

    public function setDate(\DateTimeInterface $date)
    {
        $this->date = $date;
    }

    public function getDate()
    {
        return $this->date;
    }
}

class ObjectInner
{
    public $foo;
    public $bar;
}

$normalizer = new ObjectNormalizer(null, null, null, new ReflectionExtractor());
$serializer = new Serializer([new DateTimeNormalizer(), $normalizer]);

$obj = $serializer->denormalize(
    ['inner' => ['foo' => 'foo', 'bar' => 'bar'], 'date' => '1988/01/21'],
    'Acme\ObjectOuter'
);

dump($obj->getInner()->foo); // 'foo'
dump($obj->getInner()->bar); // 'bar'
dump($obj->getDate()->format('Y-m-d')); // '1988-01-21'

When a PropertyTypeExtractor is available, the normalizer will also check that the data to denormalize matches the type of the property (even for primitive types). For instance, if a string is provided, but the type of the property is int, an :class:`Symfony\\Component\\Serializer\\Exception\\UnexpectedValueException` will be thrown. The type enforcement of the properties can be disabled by setting the serializer context option ObjectNormalizer::DISABLE_TYPE_ENFORCEMENT to true.

Serializing Interfaces and Abstract Classes

When dealing with objects that are fairly similar or share properties, you may use interfaces or abstract classes. The Serializer component allows you to serialize and deserialize these objects using a "discriminator class mapping".

The discriminator is the field (in the serialized string) used to differentiate between the possible objects. In practice, when using the Serializer component, pass a :class:`Symfony\\Component\\Serializer\\Mapping\\ClassDiscriminatorResolverInterface` implementation to the :class:`Symfony\\Component\\Serializer\\Normalizer\\ObjectNormalizer`.

The Serializer component provides an implementation of ClassDiscriminatorResolverInterface called :class:`Symfony\\Component\\Serializer\\Mapping\\ClassDiscriminatorFromClassMetadata` which uses the class metadata factory and a mapping configuration to serialize and deserialize objects of the correct class.

When using this component inside a Symfony application and the class metadata factory is enabled as explained in the :ref:`Attributes Groups section <component-serializer-attributes-groups>`, this is already set up and you only need to provide the configuration. Otherwise:

// ...
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Mapping\ClassDiscriminatorFromClassMetadata;
use Symfony\Component\Serializer\Mapping\ClassDiscriminatorMapping;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$classMetadataFactory = new ClassMetadataFactory(new AnnotationLoader(new AnnotationReader()));

$discriminator = new ClassDiscriminatorFromClassMetadata($classMetadataFactory);

$serializer = new Serializer(
    [new ObjectNormalizer($classMetadataFactory, null, null, null, $discriminator)],
    ['json' => new JsonEncoder()]
);

Now configure your discriminator class mapping. Consider an application that defines an abstract CodeRepository class extended by GitHubCodeRepository and BitBucketCodeRepository classes:

.. configuration-block::

    .. code-block:: php-annotations

        namespace App;

        use Symfony\Component\Serializer\Annotation\DiscriminatorMap;

        /**
         * @DiscriminatorMap(typeProperty="type", mapping={
         *    "github"="App\GitHubCodeRepository",
         *    "bitbucket"="App\BitBucketCodeRepository"
         * })
         */
        interface CodeRepository
        {
            // ...
        }

    .. code-block:: yaml

        App\CodeRepository:
            discriminator_map:
                type_property: type
                mapping:
                    github: 'App\GitHubCodeRepository'
                    bitbucket: 'App\BitBucketCodeRepository'

    .. code-block:: xml

        <?xml version="1.0" ?>
        <serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
                https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
        >
            <class name="App\CodeRepository">
                <discriminator-map type-property="type">
                    <mapping type="github" class="App\GitHubCodeRepository"/>
                    <mapping type="bitbucket" class="App\BitBucketCodeRepository"/>
                </discriminator-map>
            </class>
        </serializer>

Once configured, the serializer uses the mapping to pick the correct class:

$serialized = $serializer->serialize(new GitHubCodeRepository());
// {"type": "github"}

$repository = $serializer->deserialize($serialized, CodeRepository::class, 'json');
// instanceof GitHubCodeRepository

Performance

To figure which normalizer (or denormalizer) must be used to handle an object, the :class:`Symfony\\Component\\Serializer\\Serializer` class will call the :method:`Symfony\\Component\\Serializer\\Normalizer\\NormalizerInterface::supportsNormalization` (or :method:`Symfony\\Component\\Serializer\\Normalizer\\DenormalizerInterface::supportsDenormalization`) of all registered normalizers (or denormalizers) in a loop.

The result of these methods can vary depending on the object to serialize, the format and the context. That's why the result is not cached by default and can result in a significant performance bottleneck.

However, most normalizers (and denormalizers) always return the same result when the object's type and the format are the same, so the result can be cached. To do so, make those normalizers (and denormalizers) implement the :class:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface` and return true when :method:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface::hasCacheableSupportsMethod` is called.

Note

All built-in :ref:`normalizers and denormalizers <component-serializer-normalizers>` as well the ones included in API Platform natively implement this interface.

Learn more

.. toctree::
    :maxdepth: 1
    :glob:

    /serializer

.. seealso::

    Normalizers for the Symfony Serializer Component supporting popular web API formats
    (JSON-LD, GraphQL, OpenAPI, HAL, JSON:API) are available as part of the `API Platform`_ project.

.. seealso::

    A popular alternative to the Symfony Serializer component is the third-party
    library, `JMS serializer`_ (versions before ``v1.12.0`` were released under
    the Apache license, so incompatible with GPLv2 projects).

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serializer.rst

serializer.rst

The Serializer Component

Installation

Usage

Serializing an Object

Deserializing an Object

Deserializing in an Existing Object

Attributes Groups

Selecting Specific Attributes

Ignoring Attributes

Converting Property Names when Serializing and Deserializing

CamelCase to snake_case

Configure name conversion using metadata

Serializing Boolean Attributes

Using Callbacks to Serialize Properties with Object Instances

Normalizers

Encoders

Built-in Encoders

The `JsonEncoder`

The `CsvEncoder`

The `XmlEncoder`

The `YamlEncoder`

Skipping `null` Values

Handling Circular References

Handling Serialization Depth

Handling Arrays

The `XmlEncoder`

Context

Handling Constructor Arguments

Recursive Denormalization and Type Safety

Serializing Interfaces and Abstract Classes

Performance

Learn more

Files

serializer.rst

Latest commit

History

serializer.rst

File metadata and controls

The Serializer Component

Installation

Usage

Serializing an Object

Deserializing an Object

Deserializing in an Existing Object

Attributes Groups

Selecting Specific Attributes

Ignoring Attributes

Converting Property Names when Serializing and Deserializing

CamelCase to snake_case

Configure name conversion using metadata

Serializing Boolean Attributes

Using Callbacks to Serialize Properties with Object Instances

Normalizers

Encoders

Built-in Encoders

The JsonEncoder

The CsvEncoder

The XmlEncoder

The YamlEncoder

Skipping null Values

Handling Circular References

Handling Serialization Depth

Handling Arrays

The XmlEncoder

Context

Handling Constructor Arguments

Recursive Denormalization and Type Safety

Serializing Interfaces and Abstract Classes

Performance

Learn more

The `JsonEncoder`

The `CsvEncoder`

The `XmlEncoder`

The `YamlEncoder`

Skipping `null` Values

The `XmlEncoder`