php - シリアル化可能なインターフェイス

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

<?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);
    $newobj = unserialize($ser);
    var_dump($newobj->getData());
?>

string(15) "My private data"