La interfaz Serializable

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

Introducción

Interfaz para personalizar la serialización.

Las clases que implementan esta interfaz ya no admiten __sleep() ni __wakeup(). El método serialize se llama cuando una instancia requiere ser serializada. Esto no invoca a __destruct() ni tiene ningún efecto adicional a menos que se programe dentro del método. Cuando los datos son deserializados, la clase es conocida y se llama al correspondiente método unserialize() como constructor en lugar de llamar al método __construct(). Se puede ejecutar el constructor estándar en el método si fuera necesario.

Advertencia

A partir de PHP 8.1.0, una clase que implemente Serializable sin implementar también __serialize() y __unserialize() generará una advertencia de desaprobación.

Sinopsis de la Interfaz

interface Serializable {

/* Métodos */

public serialize(): ?string

public unserialize(string $data): void

}

Ejemplos

Ejemplo #1 Uso básico

<?php
class obj implements Serializable {
    private $data;
    public function __construct() {
        $this->data = "My private data";
    }
    public function serialize() {
        return serialize($this->data);
    }
    public function unserialize($data) {
        $this->data = unserialize($data);
    }
    public function getData() {
        return $this->data;
    }
}

$obj = new obj;
$ser = serialize($obj);

var_dump($ser);

$newobj = unserialize($ser);

var_dump($newobj->getData());
?>

El resultado del ejemplo sería algo similar a:

string(38) "C:3:"obj":23:{s:15:"My private data";}"
string(15) "My private data"

Tabla de contenidos

Serializable::serialize — Representación en formato cadena de un objeto
Serializable::unserialize — Construye el objeto

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User Contributed Notes 4 notes

down

grzeniufication ¶

9 years ago

Here's an example how to un-, serialize more than one property:

class Example implements \Serializable
{
    protected $property1;
    protected $property2;
    protected $property3;

    public function __construct($property1, $property2, $property3)
    {
        $this->property1 = $property1;
        $this->property2 = $property2;
        $this->property3 = $property3;
    }

    public function serialize()
    {
        return serialize([
            $this->property1,
            $this->property2,
            $this->property3,
        ]);
    }

    public function unserialize($data)
    {
        list(
            $this->property1,
            $this->property2,
            $this->property3
        ) = unserialize($data);
    }

}

down

shaun at slickdesign dot com dot au ¶

6 years ago

Serialized strings differ between instances that implement Serializable and those that don't.

Instances that don't implement Serializable use the Object notation "O:" when serialized, while those that do use the Class notation "C:". Class notation can only be used to unserialize instances that implement Serializable, while the Object notation can be used to unserialize any object.

Because of this, it is sometimes useful to implement the __wakeup() function when implementing Serializable, for instances where you may have a copy of the serialised class before it implemented Serializable (backwards compatible), or when you're expecting a serialized object from an external source, and they use Object notation for maximum compatibility. You can also use __wakeup() to process your unserialize function, or use it to help prevent people trying to bypass your unserialize.

Below is an example of a simple class hierarchy, where A is a standard class, B implements Serializable, and C uses __wakeup() to assist with unserializing it.

<?php
class A {
    protected $readonly_data = true;
    public $public_data = true;
    
    public function __construct( $data = true ) {
        $this->public_data = $data;
    }
    
    public function get_readonly_data() {
        return $this->readonly_data;
    }
}

$a = new A;

var_dump( $a );
//object(A)#1 (2) {
//  ["readonly_data":protected]=>
//  bool(true)
//  ["public_data"]=>
//  bool(true)
//}
var_dump( serialize( $a ) );
//string(63) "O:1:"A":2:{s:16:"*readonly_data";b:1;s:11:"public_data";b:1;}"
?>
Class A outputs the following object, and its serialized string uses the object notation "O:". Please note that there is a null byte "\0" either side of the star*.

Changing the serialised string and unserializing it can cause protected and private values to change.
<?php
var_dump( unserialize( "O:1:\"A\":2:{s:16:\"\0*\0readonly_data\";b:0;s:11:\"public_data\";b:0;}" ) );
//object(A)#1 (2) {
//  ["readonly_data":protected]=>
//  bool(false)
//  ["public_data"]=>
//  bool(false)
//}
?>

Class B extends A, and so has the same constructor and properties. It also implements Serializable.
<?php
class B extends A implements Serializable {
    public function serialize() {
        return serialize( $this->public_data );
    }
    
    public function unserialize( $data ) {
        $this->public_data = unserialize ( $data );
        do_extra_processing_here();
    }
}

$b = new B;

var_dump( serialize( $b ) );
// C:1:"B":4:{b:1;}
?>
As well as being a lot shorter, the serialized string uses the Class notation "C:", but you can still unserialize it using the older style notation. Doing this however will completely ignore the unserialize() function, potentially update the wrong information, and the function do_extra_processing_here() from the example above is not called.
<?php
var_dump( unserialize( "O:1:\"B\":2:{s:16:\"\0*\0readonly_data\";b:0;s:11:\"public_data\";b:0;}" ) );
//object(B)#1 (2) {
//  ["readonly_data":protected]=>
//  bool(false)
//  ["public_data"]=>
//  bool(false)
//}
?>

Class C extends B, so it's already using the serialize() and unserialize() functions. By implementing the __wakeup() method, we ensure that we are validating the information and performing our do_extra_processing_here() function.
<?php
class C extends B {
    public function __wakeup() {
        $new = new static;
        $this->readonly_data = $new->get_readonly_data();
        do_extra_processing_here();
    }
}

var_dump( unserialize( "O:1:\"C\":2:{s:16:\"\0*\0readonly_data\";b:0;s:11:\"public_data\";b:0;}" ) );
//object(B)#1 (2) {
//  ["readonly_data":protected]=>
//  bool(true)
//  ["public_data"]=>
//  bool(false)
//}
?>
We can use __wakeup() to revert our readonly data back to what it was, or to add additional processing. You can additionally call __wakeup() from within unserialize() if you need to do the same process regardless of which serialized string notation was used.

down

info at ensostudio dot ru ¶

4 years ago

Note: that interface declared as "deprecated" in PHP 7.4, use magic methods __serialize() and __unserialize() instead .

down

marcos dot gottardi at folha dot REM0VE-THIS dot com dot br ¶

12 years ago

Serializing child and parent classes:

<?php
class MyClass implements Serializable {
    private $data;
    
    public function __construct($data) {
        $this->data = $data;
    }
    
    public function getData() {
        return $this->data;
    }
    
    public function serialize() {
        echo "Serializing MyClass...\n";
        return serialize($this->data);
    }
    
    public function unserialize($data) {
        echo "Unserializing MyClass...\n";
        $this->data = unserialize($data);
    }
}

class MyChildClass extends MyClass {
    private $id;
    private $name;
    
    public function __construct($id, $name, $data) {
        parent::__construct($data);
        $this->id = $id;
        $this->name = $name;
    }
    
    public function serialize() {
        echo "Serializing MyChildClass...\n";
        return serialize(
            array(
                'id' => $this->id,
                'name' => $this->name,
                'parentData' => parent::serialize()
            )
        );
    }
    
    public function unserialize($data) {
        echo "Unserializing MyChildClass...\n";
        $data = unserialize($data);
        
        $this->id = $data['id'];
        $this->name = $data['name'];
        parent::unserialize($data['parentData']);
    }
    
    public function getId() {
        return $this->id;
    }
    
    public function getName() {
        return $this->name;
    }
}

$obj = new MyChildClass(15, 'My class name', 'My data');

$serial = serialize($obj);
$newObject = unserialize($serial);

echo $newObject->getId() . PHP_EOL;
echo $newObject->getName() . PHP_EOL;
echo $newObject->getData() . PHP_EOL;

?>

This will output:

Serializing MyChildClass...
Serializing MyClass...
Unserializing MyChildClass...
Unserializing MyClass...
15
My class name
My data

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