Object Serialization
Serializing objects - objects in sessions
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. Using serialize to save an object will save all variables in an object. The methods in an object will not be saved, only the name of the class.
In order to be able to unserialize() an object, the class of that object needs to be defined. That is, if you have an object of class A and serialize this, you'll get a string that refers to class A and contains all values of variables contained in it. If you want to be able to unserialize this in another file, an object of class A, the definition of class A must be present in that file first. This can be done for example by storing the class definition of class A in an include file and including this file or making use of the spl_autoload_register() function.
<?php
// classa.inc:
class A {
public $one = 1;
public function show_one() {
echo $this->one;
}
}
// page1.php:
include("classa.inc");
$a = new A;
$s = serialize($a);
// store $s somewhere where page2.php can find it.
file_put_contents('store', $s);
// page2.php:
// this is needed for the unserialize to work properly.
include("classa.inc");
$s = file_get_contents('store');
$a = unserialize($s);
// now use the function show_one() of the $a object.
$a->show_one();
?>
If an application is using sessions and uses session_register() to register objects, these objects are serialized automatically at the end of each PHP page, and are unserialized automatically on each of the following pages. This means that these objects can show up on any of the application's pages once they become part of the session. However, the session_register() is removed since PHP 5.4.0.
It is strongly recommended that if an application serializes objects, for use later in the application, that the application includes the class definition for that object throughout the application. Not doing so might result in an object being unserialized without a class definition, which will result in PHP giving the object a class of __PHP_Incomplete_Class_Name, which has no methods and would render the object useless.
So if in the example above $a became part of a session by running session_register("a"), you should include the file classa.inc on all of your pages, not only page1.php and page2.php.
Beyond the above advice, note that you can also hook into the serialization and unserialization events on an object using the __sleep() and __wakeup() methods. Using __sleep() also allows you to only serialize a subset of the object's properties.
- Введение
- Основы
- Свойства
- Константы классов
- Автоматическая загрузка классов
- Конструкторы и деструкторы
- Область видимости
- Наследование
- Оператор разрешения области видимости (::)
- Ключевое слово "static"
- Абстрактные классы
- Интерфейсы объектов
- Трейты
- Anonymous classes
- Перегрузка
- Итераторы объектов
- Магические методы
- Ключевое слово "final"
- Клонирование объектов
- Сравнение объектов
- Контроль типа
- Позднее статическое связывание
- Объекты и ссылки
- Сериализация объектов
- Журнал изменений ООП
Коментарии
Note that static members of an object are not serialized.Reading this page you'd be left with the impression that a class's `serialize` and `unserialize` methods are unrelated to the `serialize` and `unserialize` core functions; that only `__sleep` and `__unsleep` allow you to customize an object's serialization interface. But look at class.serializable and you'll see that there is a more straightforward way to control how a user-defined object is serialized and unserialized.Until such time as these documents are updated, note that `session_register()` is not needed to automatically serialize & unserialize objects in sessions. Any objects in `$_SESSION` are serialized when the session is closed (via `session_write_close()` or upon script exit) & unserialized when opened (via `session_start()`). The note about including classes throughout an app (either by including the definition globally or autoloading it) still holds.