The Serializable interface

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

Introdução

Interface para serialização personalizada.

Classes que implementam esta intarface não possuem mais suporte aos métodos __sleep() and __wakeup(). O método serialize é chamado não importando se uma instância possui a necessidade de ser serializada. Não invoca o método __destruct(), ou possui qualquer outro efeito colateral a não ser que programado no método. Quando os dados são deserializados, a classe toma conhecimento e o método unserialize() apropriado é chamado como um construtor, em vez de chamar o método __construct(). Se necessitar executar o construtor padrão, pode-se fazer no método.

Aviso

A partir do PHP 8.1.0, uma classe que implemente Serializable sem implementar __serialize() e __unserialize() gerará um aviso de descontinuação.

Resumo da Interface

interface Serializable {

/* Métodos */

public serialize(): ?string

public unserialize(string $data): void

}

Exemplos

Exemplo #1 Basic usage

<?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());
?>

O exemplo acima produzirá algo semelhante a:

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

Índice

Serializable::serialize — Representação em string de um objeto
Serializable::unserialize — Constrói o objeto

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Notas Enviadas por Usuários (em inglês) 4 notes

down

grzeniufication ¶

8 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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