PHP use() 函数的作用域? [英] PHP use() function for scope?

问题描述

我见过这样的代码:

function($cfg) use ($connections) {}

但 php.net 似乎没有提到该功能.我猜这与范围有关，但如何?

but php.net doesn't seem to mention that function. I'm guessing it's related to scope, but how?

推荐答案

use 不是函数，它是 闭包语法.它只是让外部作用域的指定变量在闭包内部可用.

use is not a function, it's part of the Closure syntax. It simply makes the specified variables of the outer scope available inside the closure.

$foo = 42;

$bar = function () {
    // can't access $foo in here
    echo $foo; // undefined variable
};

$baz = function () use ($foo) {
    // $foo is made available in here by use()
    echo $foo; // 42
}

例如:

$array = array('foo', 'bar', 'baz');
$prefix = uniqid();

$array = array_map(function ($elem) use ($prefix) {
    return $prefix . $elem;
}, $array);

// $array = array('4b3403665fea6foo', '4b3403665fea6bar', '4b3403665fea6baz');

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