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The Serializer Component

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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 simple schema.

As you can see in the picture above, an array is used as a man in the middle. 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 complicated topic, and while this component may not work in all cases, it can be a useful tool while developing tools to serialize and deserialize your objects.

Installation¶

You can install the component in 2 different ways:

Install it via Composer (symfony/serializer on Packagist);
Use the official Git repository (https://github.com/symfony/serializer).

Then, require the vendor/autoload.php file to enable the autoloading mechanism provided by Composer. Otherwise, your application won't be able to find the classes of this Symfony component.

Usage¶

Using the Serializer component is really simple. You just need to set up the Serializer specifying which Encoders and Normalizer are going to be available:

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

$encoders = array(new XmlEncoder(), new JsonEncoder());
$normalizers = array(new GetSetMethodNormalizer());

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

Serializing an Object¶

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

namespace Acme;

class Person
{
    private $age;
    private $name;

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

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

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

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

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

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

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

// $jsonContent contains {"name":"foo","age":99}

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

The first parameter of the serialize() is the object to be serialized and the second is used to choose the proper encoder, in this case JsonEncoder.

Ignoring Attributes when Serializing¶

New in version 2.3: The GetSetMethodNormalizer::setIgnoredAttributes method was introduced in Symfony 2.3.

As an option, there's a way to ignore attributes from the origin object when serializing. To remove those attributes use the setIgnoredAttributes() method on the normalizer definition:

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

$normalizer = new GetSetMethodNormalizer();
$normalizer->setIgnoredAttributes(array('age'));
$encoder = new JsonEncoder();

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

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:

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

$person = $serializer->deserialize($data, 'Acme\Person', 'xml');

In this case, 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

Using Camelized Method Names for Underscored Attributes¶

New in version 2.3: The GetSetMethodNormalizer::setCamelizedAttributes method was introduced in Symfony 2.3.

Sometimes property names from the serialized content are underscored (e.g. first_name). Normally, these attributes will use get/set methods like getFirst_name, when getFirstName method is what you really want. To change that behavior use the setCamelizedAttributes() method on the normalizer definition:

$encoder = new JsonEncoder();
$normalizer = new GetSetMethodNormalizer();
$normalizer->setCamelizedAttributes(array('first_name'));

$serializer = new Serializer(array($normalizer), array($encoder));

$json = <<<EOT
{
    "name":       "foo",
    "age":        "19",
    "first_name": "bar"
}
EOT;

$person = $serializer->deserialize($json, 'Acme\Person', 'json');

As a final result, the deserializer uses the first_name attribute as if it were firstName and uses the getFirstName and setFirstName methods.

Using Callbacks to Serialize Properties with Object Instances¶

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

use Acme\Person;
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
use Symfony\Component\Serializer\Serializer;

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

$callback = function ($dateTime) {
    return $dateTime instanceof \DateTime
        ? $dateTime->format(\DateTime::ISO8601)
        : '';
};

$normalizer->setCallbacks(array('createdAt' => $callback));

$serializer = new Serializer(array($normalizer), array($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"}

JMSSerializer¶

A popular third-party library, JMS serializer, provides a more sophisticated albeit more complex solution. This library includes the ability to configure how your objects should be serialized/deserialized via annotations (as well as YAML, XML and PHP), integration with the Doctrine ORM, and handling of other complex cases (e.g. circular references).

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