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.
Магические методы
Магические методы - это специальные методы, которые переопределяют действие PHP по умолчанию, когда над объектом выполняются определённые действия.
Предостережение
Все имена методов, начинающиеся с __, зарезервированы PHP.
Не рекомендуется использовать имена методов с __ в PHP, если вы не хотите использовать соответствующую
магическую функциональность.
Следующие названия методов считаются магическими: __construct(), __destruct(), __call(), __callStatic(), __get(), __set(), __isset(), __unset(), __sleep(), __wakeup(), __serialize(), __unserialize(), __toString(), __invoke(), __set_state(), __clone() и __debugInfo()
Внимание
Все магические методы, за исключением
__construct(),
__destruct() и
__clone(),
ДОЛЖНЫ быть объявлены как public,
в противном случае будет вызвана ошибка уровня E_WARNING.
До PHP 8.0.0 для магических методов
__sleep(),
__wakeup(),
__serialize(),
__unserialize() и
__set_state()
не выполнялась проверка.
Внимание
Если объявления типа используются в определении магического метода, они должны быть идентичны сигнатуре, описанной в этом документе. В противном случае выдаётся фатальная ошибка. До PHP 8.0.0 диагностические сообщения не отправлялись. Однако __construct() и __destruct() не должны объявлять возвращаемый тип; в противном случае выдаётся фатальная ошибка.
__sleep() и __wakeup()
public __sleep(): array
public __wakeup(): void
Функция serialize() проверяет, присутствует ли в
классе метод с магическим именем __sleep().
Если это так, то этот метод выполняется до любой операции сериализации. Он может
очистить объект и должен возвращать массив с именами
всех переменных этого объекта, которые должны быть сериализованы.
Если метод ничего не возвращает, то сериализуется null и
выдаётся предупреждение E_NOTICE.
Замечание:
Недопустимо возвращать в __sleep() имена закрытых свойств в родительском классе. Это приведёт к ошибке уровня
E_NOTICE. Вместо этого вы можете использовать __serialize().
Предполагаемое использование __sleep() состоит в завершении работы над данными, ждущими обработки или других подобных задач очистки. Кроме того, этот метод может быть полезен, когда есть очень большие объекты, которые нет необходимости полностью сохранять.
С другой стороны, функция unserialize() проверяет наличие метода с магическим именем __wakeup(). Если она имеется, эта функция может восстанавливать любые ресурсы, которые может иметь объект.
Предполагаемое использование __wakeup() заключается в восстановлении любых соединений с базой данных, которые могли быть потеряны во время операции сериализации и выполнения других операций повторной инициализации.
Пример #1 Сериализация и десериализация
<?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();
}
}?>
__serialize() и __unserialize()
public __serialize(): array
public __unserialize(array
$data): voidserialize() проверяет, есть ли в классе функция с магическим именем __serialize(). Если да, функция выполняется перед любой сериализацией. Она должна создать и вернуть ассоциативный массив пар ключ/значение, которые представляют сериализованную форму объекта. Если массив не возвращён, будет выдано TypeError.
Замечание:
Если и __serialize() и __sleep() определены в одном и том же объекте, будет вызван только метод __serialize(). __sleep() будет игнорироваться. Если объект реализует интерфейс Serializable, метод
serialize()интерфейса будет игнорироваться, а вместо него будет использован __serialize().
Предполагаемое использование __serialize() заключается в определении удобного для сериализации произвольного представления объекта. Элементы массива могут соответствовать свойствам объекта, но это не обязательно.
И наоборот, unserialize() проверяет наличие магической функции __unserialize(). Если функция присутствует, ей будет передан восстановленный массив, который был возвращён из __serialize(). Затем он может восстановить свойства объекта из этого массива соответствующим образом.
Замечание:
Если и __unserialize() и __wakeup() определены в одном и том же объекте, будет вызван только метод __unserialize(). __wakeup() будет игнорироваться.
Замечание:
Функция доступна с PHP 7.4.0.
Пример #2 Сериализация и десериализация
<?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 __serialize(): array
{
return [
'dsn' => $this->dsn,
'user' => $this->username,
'pass' => $this->password,
];
}
public function __unserialize(array $data): void
{
$this->dsn = $data['dsn'];
$this->username = $data['user'];
$this->password = $data['pass'];
$this->connect();
}
}?>
__toString()
public __toString(): string
Метод __toString() позволяет классу решать,
как он должен реагировать при преобразовании в
строку. Например, что вывести при выполнении echo $obj;.
Внимание
Начиная с PHP 8.0.0, возвращаемое значение следует стандартной семантике типа PHP, что означает, что оно будет преобразовано в строку (string), если возможно, и если strict typing отключён.
Начиная с PHP 8.0.0, любой класс, содержащий метод __toString(), также будет неявно реализовывать интерфейс Stringable и, таким образом, будет проходить проверку типа для этого интерфейса В любом случае рекомендуется явно реализовать интерфейс.
В PHP 7.4 возвращаемое значение ДОЛЖНО быть строкой (string), иначе выдаётся Error.
До PHP 7.4.0 возвращаемое значение должно быть
строкой (string), в противном случае выдаётся фатальная ошибка E_RECOVERABLE_ERROR.
is emitted.
Внимание
Нельзя выбросить исключение из метода __toString() до PHP 7.4.0. Это приведёт к фатальной ошибке.
Пример #3 Простой пример
<?php
// Объявление простого класса
class TestClass
{
public $foo;
public function __construct($foo)
{
$this->foo = $foo;
}
public function __toString()
{
return $this->foo;
}
}
$class = new TestClass('Привет');
echo $class;
?>
Результат выполнения данного примера:
Привет
__invoke()
Метод __invoke() вызывается, когда скрипт пытается выполнить объект как функцию.
Пример #4 Использование __invoke()
<?php
class CallableClass
{
public function __invoke($x)
{
var_dump($x);
}
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>
Результат выполнения данного примера:
int(5) bool(true)
__set_state()
static __set_state(array
$properties): objectЭтот статический метод вызывается для тех классов, которые экспортируются функцией var_export().
Единственным параметром этого метода является массив, содержащий экспортируемые
свойства в виде ['property' => value, ...].
Пример #5 Использование __set_state()
<?php
class A
{
public $var1;
public $var2;
public static function __set_state($an_array)
{
$obj = new A;
$obj->var1 = $an_array['var1'];
$obj->var2 = $an_array['var2'];
return $obj;
}
}
$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';
$b = var_export($a, true);
var_dump($b);
eval('$c = ' . $b . ';');
var_dump($c);
?>
Результат выполнения данного примера:
string(60) "A::__set_state(array(
'var1' => 5,
'var2' => 'foo',
))"
object(A)#2 (2) {
["var1"]=>
int(5)
["var2"]=>
string(3) "foo"
}
Замечание: При экспорте объекта var_export() не проверяет, реализует ли класс объекта метод __set_state(), поэтому повторный импорт объектов приведёт к исключению Error, если метод __set_state() не реализован. В частности, это относится к некоторым внутренним классам. Необходимость проверки, реализует ли импортируемый класс метод __set_state(), полностью лежит на разработчике.
__debugInfo()
__debugInfo(): array
Этот метод вызывается функцией var_dump(), когда необходимо вывести список свойств объекта. Если этот метод не определён, тогда будут выведены все свойства объекта c модификаторами public, protected и private.
Пример #6 Использование __debugInfo()
<?php
class C {
private $prop;
public function __construct($val) {
$this->prop = $val;
}
public function __debugInfo() {
return [
'propSquared' => $this->prop ** 2,
];
}
}
var_dump(new C(42));
?>
Результат выполнения данного примера:
object(C)#1 (1) {
["propSquared"]=>
int(1764)
}
add a note
User Contributed Notes 30 notes
jon at webignition dot net ¶
13 years ago
jsnell at e-normous dot com ¶
13 years ago
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)
}
*/
?>
ricasiano at gmail dot com ¶
1 year ago
Objects with __toString() passed within methods with type declarations(either from function arguments or return types) automagically converts it to string.
<?php
class Foo
{
public function __toString()
{
return 'foo';
}
}
class Bar
{
public function setAndGetFoo(string $foo)
{
return $foo;
}
public function getFoo(): string
{
return new Foo();
}
}
$foo = new Foo();
$bar = new Bar();
// string(3) "foo"
var_dump($bar->setAndGetFoo($foo));
// string(3) "foo"
var_dump($bar->getFoo());
kguest at php dot net ¶
4 years ago
__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
)
$
ctamayo at sitecrafting dot com ¶
1 year ago
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
smiley at HELLOSPAMBOT dot chillerlan dot net ¶
6 years ago
A simple API wrapper, using __call() and the PHP 5.6 "..." token.
http://php.net/manual/functions.arguments.php#functions.variable-arg-list
<?php
namespace Example;
use Exception;
use ReflectionClass;
use SomeApiInterface;
use SomeHttpClient;
use SomeEndpointHandler;
/**
* Class SomeApiWrapper
*
* @method SomeEndpointHandler method1(MethodParams $param1)
* @method SomeEndpointHandler method2(MethodParams $param1, AuthParams $param2 = null)
* ...
* @method SomeEndpointHandler method42()
*/
class SomeApiWrapper{
/**
* @var \SomeHttpClient
*/
private $httpClient;
/**
* @var array
*/
private $methodMap = [];
/**
* SomeApiWrapper constructor.
*/
public function __construct(){
$this->mapApiMethods();
$this->httpClient = new SomeHttpClient();
}
/**
* The API is flat and has ~ 150 endpoints, all of which take optional parameters
* from up to 3 groups (method params, authentication, filters). Instead of
* implementing the interface and adding countless stubs that have basically
* the same signature, i just map its methods here and use __call().
*/
private function mapApiMethods(){
$reflectionClass = new ReflectionClass(SomeApiInterface::class);
foreach($reflectionClass->getMethods() as $m){
$this->methodMap[] = $m->name;
}
}
/**
* Thanks to the PHP 5.6+ "..." token, there's no hassle with the arguments anymore
* (ugh, bad pun). Just hand the method parameters into the endpoint handler,
* along with other mandatory params - type hints are your friends.
*
* It's magic!
*
* @param string $method
* @param array $arguments
*
* @return \SomeEndpointHandler
* @throws \Exception
*/
public function __call($method, $arguments){
if(in_array($method, $this->methodMap)){
return new SomeEndpointHandler($this->httpClient, $method, ...$arguments);
}
throw new Exception('Endpoint "'.$method.'" does not exist');
}
}
daan dot broekhof at gmail dot com ¶
9 years ago
Ever wondered why you can't throw exceptions from __toString()? Yeah me too.
Well now you can! This trick allows you to throw any type of exception from within a __toString(), with a full & correct backtrace.
How does it work? Well PHP __toString() handling is not as strict in every case: throwing an Exception from __toString() triggers a fatal E_ERROR, but returning a non-string value from a __toString() triggers a non-fatal E_RECOVERABLE_ERROR.
Add a little bookkeeping, and can circumvented this PHP deficiency!
(tested to work PHP 5.3+)
<?php
set_error_handler(array('My_ToStringFixer', 'errorHandler'));
error_reporting(E_ALL | E_STRICT);
class My_ToStringFixer
{
protected static $_toStringException;
public static function errorHandler($errorNumber, $errorMessage, $errorFile, $errorLine)
{
if (isset(self::$_toStringException))
{
$exception = self::$_toStringException;
// Always unset '_toStringException', we don't want a straggler to be found later if something came between the setting and the error
self::$_toStringException = null;
if (preg_match('~^Method .*::__toString\(\) must return a string value$~', $errorMessage))
throw $exception;
}
return false;
}
public static function throwToStringException($exception)
{
// Should not occur with prescribed usage, but in case of recursion: clean out exception, return a valid string, and weep
if (isset(self::$_toStringException))
{
self::$_toStringException = null;
return '';
}
self::$_toStringException = $exception;
return null;
}
}
class My_Class
{
public function doComplexStuff()
{
throw new Exception('Oh noes!');
}
public function __toString()
{
try
{
// do your complex thing which might trigger an exception
return $this->doComplexStuff();
}
catch (Exception $e)
{
// The 'return' is required to trigger the trick
return My_ToStringFixer::throwToStringException($e);
}
}
}
$x = new My_Class();
try
{
echo $x;
}
catch (Exception $e)
{
echo 'Caught Exception! : '. $e;
}
?>
dhuseby domain getback tld com ¶
13 years ago
The above hint for using array_keys((array)$obj) got me investigating how to get __sleep to really work with object hierarchies.
With PHP 5.2.3, If you want to serialize an object that is part of an object hierarchy and you want to selectively serialize members (public, private, and protected) by manually specifying the array of members, there are a few simple rules for naming members that you must follow:
1. public members should be named using just their member name, like so:
<?php
class Foo {
public $bar;
public function __sleep() {
return array("bar");
}
}
?>
2. protected members should be named using "\0" . "*" . "\0" . member name, like so:
<?php
class Foo {
protected $bar;
public function __sleep() {
return array("\0*\0bar");
}
}
?>
3. private members should be named using "\0" . class name . "\0" . member name, like so:
<?php
class Foo {
private $bar;
public function __sleep() {
return array("\0Foo\0bar");
}
}
?>
So with this information let us serialize a class hierarchy correctly:
<?php
class Base {
private $foo = "foo_value";
protected $bar = "bar_value";
public function __sleep() {
return array("\0Base\0foo", "\0*\0bar");
}
}
class Derived extends Base {
public $baz = "baz_value";
private $boo = "boo_value";
public function __sleep() {
// we have to merge our members with our parent's
return array_merge(array("baz", "\0Derived\0boo"), parent::__sleep());
}
}
class Leaf extends Derived {
private $qux = "qux_value";
protected $zaz = "zaz_value";
public $blah = "blah_value";
public function __sleep() {
// again, merge our members with our parent's
return array_merge(array("\0Leaf\0qux", "\0*\0zaz", "blah"), parent::__sleep());
}
}
// test it
$test = new Leaf();
$s = serialize($test);
$test2 = unserialize($s);
echo $s;
print_r($test);
print_r($test2);
?>
Now if you comment out all of the __sleep() functions and output the serialized string, you will see that the output doesn't change. The most important part of course is that with the proper __sleep() functions, we can unserialize the string and get a properly set up object.
I hope this solves the mystery for everybody. __sleep() does work, if you use it correctly :-)
jeffxlevy at gmail dot com ¶
16 years ago
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).
daniel dot peder at gmail dot com ¶
3 years ago
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";
ddavenport at newagedigital dot com ¶
16 years ago
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.
martin dot goldinger at netserver dot ch ¶
16 years ago
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);
}
};
?>
rayRO ¶
15 years ago
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($wow->module);
echo('</pre>');
?>
Outputs something Like:
Constructor will have no Module Information... Use __init() instead!
--> <--
Using of __init()!
--> Guestbook <--
123
456
789
Guestbook
vali dot dr at gmail dot com ¶
11 months ago
It should be noted that if you unset a class typed property and then try to access it, __get will be called. But it MUST return the original type.
https://wiki.php.net/rfc/typed_properties_v2#overloaded_properties
Wesley ¶
10 years ago
Warning __toString can be triggerd more then one time
<?php
if(strstr(substr($obj,0,1024), 'somestuff')
echo $obj;
return 'missing somestuff at the start, create container!';
substr() will trigger a __toString aswell as echo $obj;
?>
wich cause a performance issue since it will gather all data twice.
what i used as a hotfix:
<?php
__toString(){
if(null === $this->sToString)
$this->sToString = $this->_show();
return $this->sToString;
}
?>
rudie-de-hotblocks at osu1 dot php dot net ¶
12 years ago
Note also that the constructor is executed also, and before __set_state(), making this magic function less magic, imho, (except for the ability to assign private members).
staff at pro-unreal dot de ¶
8 years ago
To avoid instanciating the parent instead of the inherited class for __set_state() as reported by jsnell, you could use late static binding introduced in PHP 5.3:
<?php
class A {
public static function __set_state($data) {
return new static();
}
}
class B extends A {
}
$instance = new B();
eval('$test = ' . var_export($instance, true) . ';');
var_dump($test);
// -> object(B)#2 (0) {
// }
?>
michal dot kocarek at seznam dot cz ¶
13 years ago
Remember that setters and getters (__set, __get) will work in your class as long as you NOT SET the property with given name.
If you still want to have the public property definition in the class source code (phpDocumentor, editor code completition, or any other reason) when using these magic methods, simply unset() your public properties inside the constructor.
__set/__get function will be called and code reader will see at first sight, which public properties are available.
Example:
<?php
class user {
/**
* @var int Gets and sets the user ID
*/
public $UserID;
private $_userID;
public function __construct() {
// All the magic is in single line:
// We unset public property, so our setters and getters
// are used and phpDoc and editors with code completition are happy
unset($this->UserID);
}
public function __set($key, $value) {
// assign value for key UserID to _userID property
}
public function __get($key) {
// return value of _userID for UserID property
}
}
?>
yanleech at gmail dot com ¶
13 years ago
Maybe we can using unserialize() & __wakeup() instead "new" when creating a new instance of class.
Consider following codes:
class foo
{
static public $WAKEUP_STR = 'O:3:"foo":0:{}';
public function foo(){}
public function bar(){}
}
$foo = unserialize(foo::$WAKEUP_STR);
Dérico Filho ¶
14 years ago
Since PHP 5.2.0, you'll always get an error like this:
"Object of class foo could not be converted to string"
When one tries to use an object as string, for instance:
class Test{}
echo new Test();
Thus, one way to avoid this problem is to programme the magic method __toString.
However, in the older versions, it would output a string saying that it was an object together a unique obj id. Therefore, the __toString() method must comply with this behaviour.
My suggestion:
class Test{
function __toString(){
if(!isset($this->__uniqid))
$this->__uniqid = md5(uniqid(rand(), true));
return(get_class($this)."@".$this->__uniqid);
}
}
echo new Test();
would output something like this:
Test@6006ba04f5569544c10a588b04849cf7
mastabog at hotmail dot com ¶
16 years ago
In reply to krisj1010 at gmail.com below:
__sleep() handles protected/private properties very well. You should never rely on get_class_vars() to retrieve property names since this function only returns the public properties. Use the Reflection API instead for that purpose. Better yet, if you know which ones you want to save it is always faster to specify the return array manually.
Anonymous ¶
11 years ago
C++-style operator overloading finally makes an appearance with the introduction to __invoke(). Unfortunately, with just '()'. In that sense, it is no more useful than having a default class method (probably quite useful actually) and not having to type out an entire method name. Complimenting wbcarts at juno dot com's point class below, the following allows calculating distance between one or more graph points...
<?php
class point {
public $x;
public $y;
function __construct($x=0, $y=0) {
$this->x = (int) $x;
$this->y = (int) $y;
}
function __invoke() {
$args = func_get_args();
$total_distance = 0;
$current_loc = $this;
foreach ($args as $arg) {
if (is_object($arg) and (get_class($arg) === get_class($this))) {
$total_distance += sqrt(pow($arg->x - $current_loc->x, 2) + pow((int) $arg->y - $current_loc->y, 2));
$current_loc = $arg;
}
else {
trigger_error("Arguments must be objects of this class.");
return;
}
}
return $total_distance;
}
}
$p1 = new point(1,1);
$p2 = new point(23,-6);
$p3 = new point(15,20);
echo $p1($p2,$p3,$p1); // round trip 73.89
?>
Functionally, __invoke() can also be used to mimic the use of variable functions. Sadly, attempting any calling of __invoke() on a static level will produce a fatal error.
krisj1010 at gmail.com ¶
17 years ago
If you are attempting to write an abstract/base class which automates the __sleep process in PHP5 you will run into some trouble if the subclasses which are being serialized have private/protected variables you need to be serialized.
The reason is, even though get_class($this) within the base class will return the subclass -- get_class_vars(get_class($this)) will *not* return the subclass' protected/private variables. Which makes sense -- using OO principles.
However, when automating __sleep it becomes necissary to have access to the private/protected subclass variables because their names have to be returned by __sleep.
So here is the work around:
<?php
public function __sleep()
{
... code ...
$sleepVars = array_keys((array)$this);
return $sleepVars;
}
?>
Even though array_keys includes more information about the variable names than just the variable names -- it still seems to work appropriately.
Anonymous ¶
11 years ago
Concerning __set() with protected/private/overloaded properties, the behavior might not be so intuitive without knowing some underlying rules. Consider this test object for the following examples...
<?php
class A {
protected $test_int = 2;
protected $test_array = array('key' => 'test');
protected $test_obj;
function __construct() {
$this->test_obj = new stdClass();
}
function __get($prop) {
return $this->$prop;
}
function __set($prop, $val) {
$this->$prop = $val;
}
}
$a = new A();
?>
Combined Operators (.=, +=, *=, etc): you must also define a companion __get() method to grant write -and- read access to the property. Remember, "$x += $y" is shorthand for "$x = $x + $y". In other words, "__set($x, (__get($x) + $y))".
Properties that are Arrays: attempting to set array values like "$a->test_array[] = 'asdf';" from outside this object will result in an "Indirect modification of overloaded property" notice and the operation completely ignored. You can't use '[]' for array value assignment in this context (with the exception only if you made __get() return by reference, in which case, it would work fine and bypass the __set() method altogether). You can work around this doing something like unioning the array instead:
<?php
$a->test_array[] = 'asdf'; // notice given and ignored unless __get() was declared to return by reference
$a->test_array += array(1 => 'asdf'); // to add a key/value
$a->test_array = array("key" => 'asdf') + $a->test_array; // to overwrite a key/value.
?>
Properties that are Objects: as long as you have that __get() method, you can freely access and alter that sub object's own properties, bypassing __set() entirely. Remember, objects are assigned and passed by reference naturally.
<?php
$a->test_obj->prop = 1; // fine if $a did not have a set method declared.
?>
All above tested in 5.3.2.
osbertv at yahoo dot com ¶
10 years ago
Invoking a class inside a class results in an error.
<?php
class A
{
public function __invoke()
{
echo "Invoking A() Class";
}
}
class B
{
public $a;
public function __construct()
{
$this->a = new A();
}
public function __invoke()
{
echo "Invoking B() Class";
}
}
$a = new A();
$b = new B();
$a();
$b();
$b->a();
?>
returns
Invoking B() Class
PHP Fatal error: Call to undefined method B::a()
Anonymous ¶
13 years ago
Serializing objects is problematic with references. This is solved redefining the __sleep() magic method. This is also problematic when parent class has private variables since the parent object is not accessible nor its private variables from within the child object.
I found a solution that seems working for classes that implements this __sleep() method, and for its subclasses. Without more work in subclasses. The inheritance system does the trick.
Recursively __sleep() call parent' __sleep() and return the whole array of variables of the object instance to be serialized.
<?php
class foo {
}
class a {
private $var1;
function __construct(foo &$obj = NULL) {
$this->var1 = &$obj;
}
/** Return its variables array, if its parent exists and the __sleep method is accessible, call it and push the result into the array and return the whole thing. */
public function __sleep() {
$a = array_keys(get_object_vars(&$this));
if (method_exists(parent, '__sleep')) {
$p = parent::__sleep();
array_push($a, $p);
};
return $a;
}
}
class b extends a {
function __construct(foo &$obj = NULL) {
parent::__construct($obj);
}
}
session_start();
$myfoo = &new foo();
$myb = &new b($myfoo);
$myb = unserialize(serialize(&$myb));
?>
This should work, I haven't tested deeper.
danillo dot paiva dot toledo at gmail dot com ¶
8 years ago
While I was studying Ruby I saw as such interesting things as properties created + its getters and setters in just one line.
I tryied to do the same in PHP and this is the code I have
class Father {
public function __call($name, $args) {
if(isset($this->$name)) {
if(isset($args[0]))
return $this->$name = $args[0];
return $this->$name;
}
return false;
}
}
class Child extends Father {
public $country = "Brazil";
public $state = "Sao Paulo";
}
Sometimes we don't need things like that on all classes but is quite interesting.
Travis Swicegood ¶
14 years ago
There is no need to use eval() to mimic mixins (i.e., multiple inheritance) within PHP 5. You only need to:
<?php
class MyClass
{
private $_obj = null;
public function __construct($obj)
{
$this->_obj = $obj;
}
public function __call($method, $args)
{
if (!method_exists($this->_obj, $method)) {
throw new Exception("unknown method [$method]");
}
return call_user_func_array(
array($this->_obj, $method),
$args
);
}
}
?>
You could just as easily add an addMixin() method that would allow you to add multiple objects to an array, and then iterate over that array until you found the right method. As noted, these are referred to as a Mixins in other languages.
docey ¶
16 years ago
about __sleep and _wakeup, consider using a method like this:
class core
{
var $sub_core; //ref of subcore
var $_sleep_subcore; // place where serialize version of sub_core will be stored
function core(){
$this->sub_core = new sub_core();
return true;
}
function __wakeup()
{
// on wakeup of core, core unserializes sub_core
// wich it had stored when it was serialized itself
$this->sub_core = unserialize($this->_sleep_subcore);
return true;
}
function __sleep()
{
// sub_core will be serialized when core is serialized.
// the serialized subcore will be stored as a string inside core.
$this->_sleep_subcore = serialize($this->sub_core);
$return_arr[] = "_sleep_subcore";
return $return_arr;
}
}
class sub_core
{
var $info;
function sub_core()
{
$this->info["somedata"] = "somedata overhere"
}
function __wakeup()
{
return true;
}
function __sleep()
{
$return_arr[] = "info"
return $return_arr;
}
}
this way subcore is being serialized by core when core is being serialized. subcore handles its own data and core stores it as a serialize string inside itself. on wakeup core unserializes subcore.
this may have a performance cost, but if you have many objects connected this way this is the best way of serializing them. you only need to serialize the the main object wich will serialize all those below which will serialize all those below them again. in effect causing a sort of chainreaction in wich each object takes care of its own info.
offcoarse you always need to store the eventualy serialized string in a safe place. somebody got experience with this way of __wakeup and __sleep.
works in PHP4&5
tom ¶
11 years ago
Note a common pitfall when using __wakeup.
If you unserialize a datastructure, you may not rely on the parent object to have been fully unserialized by the time __wakeup is called. Example
<?php
class A {
public $b;
public $name;
}
class B extends A {
public $parent;
public function __wakeup() {
var_dump($parent->name);
}
}
$a = new A();
$a->name = "foo";
$a->b = new B();
$a->b->parent = $a;
$s = serialize($a);
$a = unserialize($s);
?>
Expected output: "foo".
Actual output: NULL.
Reason: $b is unserialized before $name. By the time B::__wakeup is called, $a->name does not yet have a value.
So be aware that the order in which your class variables are defined is important! You need to manually order them by dependencies - or write a __sleep function and order them by depencies there. (Currently I can't tell which option I hate more)
