Object Serialization

Syntax

  • serialize($object)
  • unserialize($object)

Remarks

All PHP types except for resources are serializable. Resources are a unique variable type that reference "external" sources, such as database connections.

Serialize / Unserialize

serialize() returns a string containing a byte-stream representation of any value that can be stored in PHP. unserialize() can use this string to recreate the original variable values.

To serialize an object

serialize($object);

To Unserialize an object

unserialize($object)

Example

$array = array();
$array["a"] = "Foo";
$array["b"] = "Bar";
$array["c"] = "Baz";
$array["d"] = "Wom";

$serializedArray = serialize($array);
echo $serializedArray; //output: a:4:{s:1:"a";s:3:"Foo";s:1:"b";s:3:"Bar";s:1:"c";s:3:"Baz";s:1:"d";s:3:"Wom";}

The Serializable interface

Introduction

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.

Basic usage

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

$newobj = unserialize($ser);

var_dump($newobj->getData()); // Output: string(15) "My private data"