(PHP 5 >= 5.1.0, PHP 7)
Examples:
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::unserialize

(PHP 5 >= 5.1.0, PHP 7) Constructs the object

2016-02-24 15:53:34
Serializable::serialize

(PHP 5 >= 5.1.0, PHP 7) String representation of object

2016-02-24 15:53:34