Serializable 인터페이스

(PHP 5 >= 5.1.0, PHP 7)

소개

커스텀 직렬화를 위한 인터페이스 입니다.

이 인터페이스를 구현한 클래스는 더이상 __sleep()__wakeup() 를 지원하지 않습니다. serialize 메서드는 인스턴스의 직렬화 필요시 언제든지 호출됩니다. 이 메서드는 __destruct() 를 호출하지 않습니다. 또한 메서드 내부에서 호출하지 않는이상 어떤 부작용도 없습니다. 데이터가 역직렬화 될때 클래스는 자동으로 __construct() 대신에 unserialize() 메서드를 호출합니다. 만약에 표준생성자를 실행하고 싶다면, unserialize() 메서드 내부에서 하시면 됩니다.

인터페이스 개요

Serializable {
/* 메소드 */
abstract public string serialize ( void )
abstract public void unserialize ( string $serialized )
}

Example #1 기초 사용법

<?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());
?>

위 예제의 출력 예시:

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

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User Contributed Notes 6 notes

up
64
grzeniufication
4 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);
    }

}
up
7
shaun at slickdesign dot com dot au
2 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.
up
-5
marcos dot gottardi at folha dot REM0VE-THIS dot com dot br
8 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
up
-5
Olivier Pons
6 years 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).
up
-5
Wojciech Brozyna
3 years ago
My solution that let you serialize inherited objects.
Without specify what need to be serialized.
We want to get rid of PDO object in this example.

abstract class DefaultModel() implements \Serializable
{

    /**
    * @var PDO
    */
    private $pdo;

    /**
     * Serialize object
     *
     * @return string
     */
    public function serialize()
    {
       
        $serializable = get_object_vars($this);
       
        // unset property name that hold PDO instance
        unset($serializable['pdo']);
       
        return serialize($serializable);
       
    }

    /**
     * Unserialize object
     *
     * @param string $serialized Serialized object
     * @return DefaultModel
     */
    public function unserialize($serialized)
    {
       
        $unserialized = unserialize($serialized);
       
       // recreate PDO object
        $this->pdo = $this->createDBObject();
       
        if(is_array($unserialized) === true) {
           
            foreach($unserialized as $property => $value) {
               
                $this->{$property} = $value;
               
            }
           
        }
       
    }

}

class RealModel extends DefaultModel
{

    private $myVar;

    public function setMyVar($value)
    {

        $this->myVar = $value;

    }

}

$model = new RealModel();
$model->setMyVar('123456');

$serialized = serialize($model);
$serialized = $model->serialize();   // will also work

print_r($serialized);

$unserialized = unserialize($serialized);

print_r($unserialized);

Hope this help.
up
-16
Anonymous
9 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.
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