Anonymous classes
Support for anonymous classes was added in PHP 7. Anonymous classes are useful when simple, one-off objects need to be created.
<?php
// Pre PHP 7 code
class Logger
{
public function log($msg)
{
echo $msg;
}
}
$util->setLogger(new Logger());
// PHP 7+ code
$util->setLogger(new class {
public function log($msg)
{
echo $msg;
}
});
They can pass arguments through to their constructors, extend other classes, implement interfaces, and use traits just like a normal class can:
<?php
class SomeClass {}
interface SomeInterface {}
trait SomeTrait {}
var_dump(new class(10) extends SomeClass implements SomeInterface {
private $num;
public function __construct($num)
{
$this->num = $num;
}
use SomeTrait;
});
Результат выполнения данного примера:
object(class@anonymous)#1 (1) {
["Command line code0x104c5b612":"class@anonymous":private]=>
int(10)
}
Nesting an anonymous class within another class does not give it access to any private or protected methods or properties of that outer class. In order to use the outer class' protected properties or methods, the anonymous class can extend the outer class. To use the private properties of the outer class in the anonymous class, they must be passed through its constructor:
<?php
class Outer
{
private $prop = 1;
protected $prop2 = 2;
protected function func1()
{
return 3;
}
public function func2()
{
return new class($this->prop) extends Outer {
private $prop3;
public function __construct($prop)
{
$this->prop3 = $prop;
}
public function func3()
{
return $this->prop2 + $this->prop3 + $this->func1();
}
};
}
}
echo (new Outer)->func2()->func3();
Результат выполнения данного примера:
6
All objects created by the same anonymous class declaration are instances of that very class.
<?php
function anonymous_class()
{
return new class {};
}
if (get_class(anonymous_class()) === get_class(anonymous_class())) {
echo 'same class';
} else {
echo 'different class';
}
Результат выполнения данного примера:
same class
Замечание:
Note that anonymous classes are assigned a name by the engine, as demonstrated in the following example. This name has to be regarded an implementation detail, which should not be relied upon.
<?php
echo get_class(new class {});Результатом выполнения данного примера будет что-то подобное:
class@anonymous/in/oNi1A0x7f8636ad2021
- 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
Below three examples describe anonymous class with very simple and basic but quite understandable example
<?php
// First way - anonymous class assigned directly to variable
$ano_class_obj = new class{
public $prop1 = 'hello';
public $prop2 = 754;
const SETT = 'some config';
public function getValue()
{
// do some operation
return 'some returned value';
}
public function getValueWithArgu($str)
{
// do some operation
return 'returned value is '.$str;
}
};
echo "\n";
var_dump($ano_class_obj);
echo "\n";
echo $ano_class_obj->prop1;
echo "\n";
echo $ano_class_obj->prop2;
echo "\n";
echo $ano_class_obj::SETT;
echo "\n";
echo $ano_class_obj->getValue();
echo "\n";
echo $ano_class_obj->getValueWithArgu('OOP');
echo "\n";
echo "\n";
// Second way - anonymous class assigned to variable via defined function
$ano_class_obj_with_func = ano_func();
function ano_func()
{
return new class {
public $prop1 = 'hello';
public $prop2 = 754;
const SETT = 'some config';
public function getValue()
{
// do some operation
return 'some returned value';
}
public function getValueWithArgu($str)
{
// do some operation
return 'returned value is '.$str;
}
};
}
echo "\n";
var_dump($ano_class_obj_with_func);
echo "\n";
echo $ano_class_obj_with_func->prop1;
echo "\n";
echo $ano_class_obj_with_func->prop2;
echo "\n";
echo $ano_class_obj_with_func::SETT;
echo "\n";
echo $ano_class_obj_with_func->getValue();
echo "\n";
echo $ano_class_obj_with_func->getValueWithArgu('OOP');
echo "\n";
echo "\n";
// Third way - passing argument to anonymous class via constructors
$arg = 1; // we got it by some operation
$config = [2, false]; // we got it by some operation
$ano_class_obj_with_arg = ano_func_with_arg($arg, $config);
function ano_func_with_arg($arg, $config)
{
return new class($arg, $config) {
public $prop1 = 'hello';
public $prop2 = 754;
public $prop3, $config;
const SETT = 'some config';
public function __construct($arg, $config)
{
$this->prop3 = $arg;
$this->config =$config;
}
public function getValue()
{
// do some operation
return 'some returned value';
}
public function getValueWithArgu($str)
{
// do some operation
return 'returned value is '.$str;
}
};
}
echo "\n";
var_dump($ano_class_obj_with_arg);
echo "\n";
echo $ano_class_obj_with_arg->prop1;
echo "\n";
echo $ano_class_obj_with_arg->prop2;
echo "\n";
echo $ano_class_obj_with_arg::SETT;
echo "\n";
echo $ano_class_obj_with_arg->getValue();
echo "\n";
echo $ano_class_obj_with_arg->getValueWithArgu('OOP');
echo "\n";
echo "\n";
Please note that class name returned by `get_class` might contain null bytes, as is the case in my version of PHP (7.1.4).
Name will change when class starting line or it's body is changed.
Yes, name is implementation detail that should not be relied upon, but in some rare use cases it is required (annotating anonymous class).
Anonymous classes are syntax sugar that may appear deceiving to some.
The 'anonymous' class is still parsed into the global scope, where it is auto assigned a name, and every time the class is needed, that global class definition is used. Example to illustrate....
The anonymous class version...
<?php
function return_anon(){
return new class{
public static $str="foo";
};
}
$test=return_anon();
echo $test::$str; //ouputs foo
//we can still access the 'anon' class directly in the global scope!
$another=get_class($test); //get the auto assigned name
echo $another::$str; //outputs foo
?>
The above is functionally the same as doing this....
<?php
class I_named_this_one{
public static $str="foo";
}
function return_not_anon(){
return 'I_named_this_one';
}
$clzz=return_not_anon();//get class name
echo $clzz::$str;
?>
/* I like the idea of OneShot classes.
Thanks to that Anonymous bro\sist for precising
new class( $a, $b )
¯¯¯¯¯¯¯¯¯
If you are looking for "Delayed OneShot Anonymous Classes" for any reason (like the reason: loading files in a readable manner while not using autoload), it would probably look something like this; */
$u = function()use(&$u){
$u = new class{private $name = 'Utils';};
};
$w = function(&$rewrite)use(&$w){
$w = null;
$rewrite = new class{private $name = 'DataUtils';};
};
// Usage;
var_dump(
array(
'Delayed',
'( Self Destructive )',
'Anonymous Class Creation',
array(
'Before ( $u )' => $u,
'Running ( $u() )' => $u(),
'After ( $u )' => $u,
),
0,0,
0,0,
0,0,
'Delayed',
'( Overwriting && Self Destructive )',
'Anonymous Class Creation',
array(
'Before ( $w )' => $w,
'Running ( $w($u) )' => $w($u),
'After ( $w )' => $w,
'After ( $u )' => $u
)
)
);
// btw : oh shoot I failed a spam challenge
I wanted to share my findings on static properties of anonymous classes.
So, given an anonymous class' object generating function like this:
<?php
function nc () {
return new class {
public static $prop = [];
};
}
?>
Getting a new object and changing the static property:
<?php
$a = nc();
$a::$prop[] = 'a';
var_dump($a::$prop);
// array(1) {
// [0] =>
// string(1) "a"
// }
?>
Now getting another object and changing the static property will change the original one, meaning that the static property is truly static:
<?php
$b = nc();
$b::$prop[] = 'b';
var_dump($b::$prop); // Same as var_dump($a::$prop);
// array(2) {
// [0] =>
// string(1) "a"
// [1] =>
// string(1) "b"
// }
assert($a::$prop === $b::$prop); // true
?>
The only way to type hint this would appear to be as object.
If you need multiple instances of an anonymous class in a function you can use:
$class = function(string $arg):object {
return new class($arg) {
public function __construct(string $arg) {
$this->ow = $arg;
}
};
};
Though for the sake of structure it's ill advised to do something like this outside of a single scope or that's used across multiple files. If you class is only used in one scope however then it's probably not a code mess problem.
you can try these
<?php
$oracle=&$_['nice_php'];
$_['nice_php']=(function(){
return new class{
public static function say($msg){
echo $msg;
}
public static function sp(){
echo self::say(' ');
}
};
});
/*
$_['nice_php']()::say('Hello');
$_['nice_php']()::sp();
$_['nice_php']()::say('World');
$_['nice_php']()::sp();
$_['nice_php']()::say('!');
//almost the same code bottom
*/
$oracle()::say('Hello');
$oracle()::sp();
$oracle()::say('World');
$oracle()::sp();
$oracle()::say('!');
?>
Thanks to the new property hooks in PHP 8.4 (https://wiki.php.net/rfc/property-hooks) and anonymous functions, now we can create an inner class instantiated only on use:
<?php
class BaseClass {
public function __construct() { echo "base class\n"; }
public $childClass { set {} get {
if ($this->childClass === null ) {
$this->childClass = new class {
public function __construct() { echo " child class\n"; }
public function say(string $s) : void { echo " $s\n"; }
};
}
return $this->childClass;
}
}
}
$base = new BaseClass();
$base->childClass->say('Hello');
$base->childClass->say('World');
/*
Output:
base class
child class
Hello
World
*/
?>
The obvious downside is that you can't set a type to the child class, unless you define an interface and the child class implements it or if the child class extends an existing class:
<?php
class ParentClass {
public function say(string $s) : void { echo " $s\n"; }
}
class BaseClass {
public function __construct() { echo "base class\n"; }
public ParentClass $childClass { set {} get {
if (!isset($this->childClass)) {
$this->childClass = new class extends ParentClass {
public function __construct() { echo " child class\n"; }
};
}
return $this->childClass;
}
}
}
$base = new BaseClass();
$base->childClass->say('Hello');
$base->childClass->say('World');
/*
Output:
base class
child class
Hello
World
*/
?>
?>
This can be also done with functions, but with hooks to me looks more like in other languages that have this functionality natively.