Magic Methods
The function names __construct(), __destruct(), __call(), __callStatic(), __get(), __set(), __isset(), __unset(), __sleep(), __wakeup(), __toString(), __invoke(), __set_state() and __clone() are magical in PHP classes. You cannot have functions with these names in any of your classes unless you want the magic functionality associated with them.
PHP reserves all function names starting with __ as magical. It is recommended that you do not use function names with __ in PHP unless you want some documented magic functionality.
__sleep() and __wakeup()
serialize() checks if your class has a function with
the magic name __sleep(). If so, that function is
executed prior to any serialization. It can clean up the object
and is supposed to return an array with the names of all variables
of that object that should be serialized.
If the method doesn't return anything then NULL is serialized and
E_NOTICE is issued.
Note:
It is not possible for __sleep() to return names of private properties in parent classes. Doing this will result in an
E_NOTICElevel error. Instead you may use the Serializable interface.
The intended use of __sleep() is to commit pending data or perform similar cleanup tasks. Also, the function is useful if you have very large objects which do not need to be saved completely.
Conversely, unserialize() checks for the presence of a function with the magic name __wakeup(). If present, this function can reconstruct any resources that the object may have.
The intended use of __wakeup() is to reestablish any database connections that may have been lost during serialization and perform other reinitialization tasks.
Example #1 Sleep and wakeup
<?php
class Connection
{
protected $link;
private $dsn, $username, $password;
public function __construct($dsn, $username, $password)
{
$this->dsn = $dsn;
$this->username = $username;
$this->password = $password;
$this->connect();
}
private function connect()
{
$this->link = new PDO($this->dsn, $this->username, $this->password);
}
public function __sleep()
{
return array('dsn', 'username', 'password');
}
public function __wakeup()
{
$this->connect();
}
}?>
__toString()
The __toString() method allows a class to decide
how it will react when it is treated like a string. For example,
what echo $obj; will print. This method must
return a string, as otherwise a fatal E_RECOVERABLE_ERROR
level error is emitted.
You cannot throw an exception from within a __toString() method. Doing so will result in a fatal error.
Example #2 Simple example
<?php
// Declare a simple class
class TestClass
{
public $foo;
public function __construct($foo)
{
$this->foo = $foo;
}
public function __toString()
{
return $this->foo;
}
}
$class = new TestClass('Hello');
echo $class;
?>
The above example will output:
Hello
It is worth noting that before PHP 5.2.0 the __toString()
method was only called when it was directly combined with
echo or print.
Since PHP 5.2.0, it is called in any string context (e.g. in
printf() with %s modifier) but not
in other types contexts (e.g. with %d modifier).
Since PHP 5.2.0, converting objects without __toString()
method to string would cause E_RECOVERABLE_ERROR.
__invoke()
The __invoke() method is called when a script tries to call an object as a function.
Note:
This feature is available since PHP 5.3.0.
Example #3 Using __invoke()
<?php
class CallableClass
{
public function __invoke($x)
{
var_dump($x);
}
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>
The above example will output:
int(5) bool(true)
__set_state()
$properties
)This static method is called for classes exported by var_export() since PHP 5.1.0.
The only parameter of this method is an array containing exported properties in the form array('property' => value, ...).
Example #4 Using __set_state() (since PHP 5.1.0)
<?php
class A
{
public $var1;
public $var2;
public static function __set_state($an_array) // As of PHP 5.1.0
{
$obj = new A;
$obj->var1 = $an_array['var1'];
$obj->var2 = $an_array['var2'];
return $obj;
}
}
$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';
eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
// 'var1' => 5,
// 'var2' => 'foo',
// ));
var_dump($b);
?>
The above example will output:
object(A)#2 (2) {
["var1"]=>
int(5)
["var2"]=>
string(3) "foo"
}
- 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
One of the principles of OOP is encapsulation--the idea that an object should handle its own data and no others'. Asking base classes to take care of subclasses' data, esp considering that a class can't possibly know how many dozens of ways it will be extended, is irresponsible and dangerous.
Consider the following...
<?php
class SomeStupidStorageClass
{
public function getContents($pos, $len) { ...stuff... }
}
class CryptedStorageClass extends SomeStupidStorageClass
{
private $decrypted_block;
public function getContents($pos, $len) { ...decrypt... }
}
?>
If SomeStupidStorageClass decided to serialize its subclasses' data as well as its own, a portion of what was once an encrypted thingie could be stored, in the clear, wherever the thingie was stored. Obviously, CryptedStorageClass would never have chosen this...but it had to either know how to serialize its parent class's data without calling parent::_sleep(), or let the base class do what it wanted to.
Considering encapsulation again, no class should have to know how the parent handles its own private data. And it certainly shouldn't have to worry that users will find a way to break access controls in the name of convenience.
If a class wants both to have private/protected data and to survive serialization, it should have its own __sleep() method which asks the parent to report its own fields and then adds to the list if applicable. Like so....
<?php
class BetterClass
{
private $content;
public function __sleep()
{
return array('basedata1', 'basedata2');
}
public function getContents() { ...stuff... }
}
class BetterDerivedClass extends BetterClass
{
private $decrypted_block;
public function __sleep()
{
return parent::__sleep();
}
public function getContents() { ...decrypt... }
}
?>
The derived class has better control over its data, and we don't have to worry about something being stored that shouldn't be.
Intriguing what happens when __sleep() and __wakeup() and sessions() are mixed. I had a hunch that, as session data is serialized, __sleep would be called when an object, or whatever, is stored in _SESSION. true. The same hunch applied when session_start() was called. Would __wakeup() be called? True. Very helpful, specifically as I'm building massive objects (well, lots of simple objects stored in sessions), and need lots of automated tasks (potentially) reloaded at "wakeup" time. (for instance, restarting a database session/connection).When you use sessions, its very important to keep the sessiondata small, due to low performance with unserialize. Every class shoud extend from this class. The result will be, that no null Values are written to the sessiondata. It will increase performance.
<?
class BaseObject
{
function __sleep()
{
$vars = (array)$this;
foreach ($vars as $key => $val)
{
if (is_null($val))
{
unset($vars[$key]);
}
}
return array_keys($vars);
}
};
?>
If you use the Magical Method '__set()', be shure that the call of
<?php
$myobject->test['myarray'] = 'data';
?>
will not appear!
For that u have to do it the fine way if you want to use __set Method ;)
<?php
$myobject->test = array('myarray' => 'data');
?>
If a Variable is already set, the __set Magic Method already wont appear!
My first solution was to use a Caller Class.
With that, i ever knew which Module i currently use!
But who needs it... :]
There are quiet better solutions for this...
Here's the Code:
<?php
class Caller {
public $caller;
public $module;
function __call($funcname, $args = array()) {
$this->setModuleInformation();
if (is_object($this->caller) && function_exists('call_user_func_array'))
$return = call_user_func_array(array(&$this->caller, $funcname), $args);
else
trigger_error("Call to Function with call_user_func_array failed", E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function __construct($callerClassName = false, $callerModuleName = 'Webboard') {
if ($callerClassName == false)
trigger_error('No Classname', E_USER_ERROR);
$this->module = $callerModuleName;
if (class_exists($callerClassName))
$this->caller = new $callerClassName();
else
trigger_error('Class not exists: \''.$callerClassName.'\'', E_USER_ERROR);
if (is_object($this->caller))
{
$this->setModuleInformation();
if (method_exists($this->caller, '__init'))
$this->caller->__init();
$this->unsetModuleInformation();
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
}
function __destruct() {
$this->setModuleInformation();
if (method_exists($this->caller, '__deinit'))
$this->caller->__deinit();
$this->unsetModuleInformation();
}
function __isset($isset) {
$this->setModuleInformation();
if (is_object($this->caller))
$return = isset($this->caller->{$isset});
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function __unset($unset) {
$this->setModuleInformation();
if (is_object($this->caller)) {
if (isset($this->caller->{$unset}))
unset($this->caller->{$unset});
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
}
function __set($set, $val) {
$this->setModuleInformation();
if (is_object($this->caller))
$this->caller->{$set} = $val;
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
}
function __get($get) {
$this->setModuleInformation();
if (is_object($this->caller)) {
if (isset($this->caller->{$get}))
$return = $this->caller->{$get};
else
$return = false;
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function setModuleInformation() {
$this->caller->module = $this->module;
}
function unsetModuleInformation() {
$this->caller->module = NULL;
}
}
// Well this can be a Config Class?
class Config {
public $module;
public $test;
function __construct()
{
print('Constructor will have no Module Information... Use __init() instead!<br />');
print('--> '.print_r($this->module, 1).' <--');
print('<br />');
print('<br />');
$this->test = '123';
}
function __init()
{
print('Using of __init()!<br />');
print('--> '.print_r($this->module, 1).' <--');
print('<br />');
print('<br />');
}
function testFunction($test = false)
{
if ($test != false)
$this->test = $test;
}
}
echo('<pre>');
$wow = new Caller('Config', 'Guestbook');
print_r($wow->test);
print('<br />');
print('<br />');
$wow->test = '456';
print_r($wow->test);
print('<br />');
print('<br />');
$wow->testFunction('789');
print_r($wow->test);
print('<br />');
print('<br />');
print_r($wow->module);
echo('</pre>');
?>
Outputs something Like:
Constructor will have no Module Information... Use __init() instead!
--> <--
Using of __init()!
--> Guestbook <--
123
456
789
Guestbook
The __toString() method is extremely useful for converting class attribute names and values into common string representations of data (of which there are many choices). I mention this as previous references to __toString() refer only to debugging uses.
I have previously used the __toString() method in the following ways:
- representing a data-holding object as:
- XML
- raw POST data
- a GET query string
- header name:value pairs
- representing a custom mail object as an actual email (headers then body, all correctly represented)
When creating a class, consider what possible standard string representations are available and, of those, which would be the most relevant with respect to the purpose of the class.
Being able to represent data-holding objects in standardised string forms makes it much easier for your internal representations of data to be shared in an interoperable way with other applications.
Be very careful to define __set_state() in classes which inherit from a parent using it, as the static __set_state() call will be called for any children. If you are not careful, you will end up with an object of the wrong type. Here is an example:
<?php
class A
{
public $var1;
public static function __set_state($an_array)
{
$obj = new A;
$obj->var1 = $an_array['var1'];
return $obj;
}
}
class B extends A {
}
$b = new B;
$b->var1 = 5;
eval('$new_b = ' . var_export($b, true) . ';');
var_dump($new_b);
/*
object(A)#2 (1) {
["var1"]=>
int(5)
}
*/
?>
__debugInfo is also utilised when calling print_r on an object:
$ cat test.php
<?php
class FooQ {
private $bar = '';
public function __construct($val) {
$this->bar = $val;
}
public function __debugInfo()
{
return ['_bar' => $this->bar];
}
}
$fooq = new FooQ("q");
print_r ($fooq);
$ php test.php
FooQ Object
(
[_bar] => q
)
$
http://sandbox.onlinephpfunctions.com/code/4d2cc3648aed58c0dad90c7868173a4775e5ba0c
IMHO a bug or need feature change
providing a object as a array index doesn't try to us __toString() method so some volatile object identifier is used to index the array, which is breaking any persistency. Type hinting solves that, but while other than "string" type hinting doesn't work on ob jects, the automatic conversion to string should be very intuitive.
PS: tried to submit bug, but withot patch the bugs are ignored, unfortunately, I don't C coding
<?php
class shop_product_id {
protected $shop_name;
protected $product_id;
function __construct($shop_name,$product_id){
$this->shop_name = $shop_name;
$this->product_id = $product_id;
}
function __toString(){
return $this->shop_name . ':' . $this->product_id;
}
}
$shop_name = 'Shop_A';
$product_id = 123;
$demo_id = $shop_name . ':' . $product_id;
$demo_name = 'Some product in shop A';
$all_products = [ $demo_id => $demo_name ];
$pid = new shop_product_id( $shop_name, $product_id );
echo "with type hinting: ";
echo ($demo_name === $all_products[(string)$pid]) ? "ok" : "fail";
echo "\n";
echo "without type hinting: ";
echo ($demo_name === $all_products[$pid]) ? "ok" : "fail";
echo "\n";
Due to a bug in PHP <= 7.3, overriding the __debugInfo() method from SPL classes is silently ignored.
<?php
class Debuggable extends ArrayObject {
public function __debugInfo() {
return ['special' => 'This should show up'];
}
}
var_dump(new Debuggable());
// Expected output:
// object(Debuggable)#1 (1) {
// ["special"]=>
// string(19) "This should show up"
// }
// Actual output:
// object(Debuggable)#1 (1) {
// ["storage":"ArrayObject":private]=>
// array(0) {
// }
// }
?>
Bug report: https://bugs.php.net/bug.php?id=69264
Please note that as of PHP 8.2 implementing __serialize() has no control over the output of json_encode(). you still have to implement JsonSerializable.