The Serializable interface

(PHP 5 >= 5.1.0, PHP 7)

Introduction

Interface for customized serializing.

Classes that implement this interface no longer support __sleep() and __wakeup(). The method serialize is called whenever an instance needs to be serialized. This does not invoke __destruct() or has any other side effect unless programmed inside the method. When the data is unserialized the class is known and the appropriate unserialize() method is called as a constructor instead of calling __construct(). If you need to execute the standard constructor you may do so in the method.

Interface synopsis

Serializable {

/* Methods */

abstract public string serialize ( void )

abstract public void unserialize ( string $serialized )

}

Example #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());
?>

The above example will output something similar to:

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

Serializable::serialize — String representation of object
Serializable::unserialize — Constructs the object

User Contributed Notes

grzeniufication

5 months 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);
    }

}

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

4 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

Anonymous

4 years ago


You can prevent an object getting unserialized by returning NULL. Instead of a serialized object, PHP will return the serialized form of NULL:

<?php
class testNull implements Serializable {
    public function serialize() {        
        return NULL;
    }
    public function unserialize($data) {
    }
}

$obj = new testNull;
$string = serialize($obj);
echo $string; // "N;"
?>

That's perhaps better than throwing exceptions inside of the serialize function if you want to prevent serialization of certain objects.

Olivier Pons

1 year ago


Here's the way you could implement serializable so that *ALL* descendant serialize themselves without the need of re-writing for all descendant the functions serialize() and unserialize().

Note : this will only serialize "visible" properties, this it won't serialize private descendant properties. If you dont want a property of a descendant to be serialized, make it private.

class Pot implements Serializable
{
    protected $_a;
    protected $_b;

    public function serialize()
    {
        return serialize(get_object_vars($this));
    }
    public function unserialize($data)
    {
        $values = unserialize($data);
        foreach ($values as $key=>$value) {
            $this->$key = $value;
        }
    }
}

And now one descendant:

class PotId implements Pot
{
    protected $_k;
}

class Pots implements PotId
{
    protected $_l;
}

$pots = new Pots();

and calling serialize($pots) will serialize all properties ($_a, $_b, $_k, $l).

The Serializable interface

Introduction

Interface synopsis

Table of Contents

User Contributed Notes