This caused me some confusion a while back when I was still learning what closures were and how to use them, but what is referred to as a closure in PHP isn't the same thing as what they call closures in other languages (E.G. JavaScript).
In JavaScript, a closure can be thought of as a scope, when you define a function, it silently inherits the scope it's defined in, which is called its closure, and it retains that no matter where it's used. It's possible for multiple functions to share the same closure, and they can have access to multiple closures as long as they are within their accessible scope.
In PHP, a closure is a callable class, to which you've bound your parameters manually.
It's a slight distinction but one I feel bears mentioning.
Класс Closure
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
Введение
Класс, используемый для создания анонимных функций.
Анонимные функции выдают объекты этого типа. Класс получил методы, позволяющие контролировать анонимную функцию после её создания.
Кроме методов, описанных здесь, этот класс также имеет метод __invoke.
Данный метод необходим только для совместимости с другими классами, в которых
реализован магический вызов, так как
этот метод не используется при вызове функции.
Содержание
- Closure::__construct — Конструктор, запрещающий создание экземпляра
- Closure::bind — Дублирует замыкание с указанием конкретного связанного объекта и области видимости класса
- Closure::bindTo — Дублирует замыкание с указанием связанного объекта и области видимости класса
- Closure::call — Связывает и запускает замыкание
- Closure::fromCallable — Конвертирует callable в замыкание
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User Contributed Notes 4 notes
chuck at bajax dot us ¶
9 years ago
joe dot scylla at gmail dot com ¶
8 years ago
Small little trick. You can use a closures in itself via reference.
Example to delete a directory with all subdirectories and files:
<?php
$deleteDirectory = null;
$deleteDirectory = function($path) use (&$deleteDirectory) {
$resource = opendir($path);
while (($item = readdir($resource)) !== false) {
if ($item !== "." && $item !== "..") {
if (is_dir($path . "/" . $item)) {
$deleteDirectory($path . "/" . $item);
} else {
unlink($path . "/" . $item);
}
}
}
closedir($resource);
rmdir($path);
};
$deleteDirectory("path/to/directoy");
?>
luk4z_7 at hotmail dot com ¶
9 years ago
Scope
A closure encapsulates its scope, meaning that it has no access to the scope in which it is defined or executed. It is, however, possible to inherit variables from the parent scope (where the closure is defined) into the closure with the use keyword:
function createGreeter($who) {
return function() use ($who) {
echo "Hello $who";
};
}
$greeter = createGreeter("World");
$greeter(); // Hello World
This inherits the variables by-value, that is, a copy is made available inside the closure using its original name.
font: Zend Certification Study Guide.
info at ensostudio dot ru ¶
2 years ago
compare closures:
<?php
(string) new ReflectionFunction($fn) === (string) new ReflectionFunction($fn2)
?>
