PHP - 'use()' 或 'global' 之间的区别来访问闭包中的全局变量? [英] PHP - Difference between 'use()' or 'global' to access a global variable in a closure?

问题描述

以下两种访问闭包中的全局变量的情况之间是否有任何性能或其他差异:

Is there any kind of performance or other difference between following two cases of accessing a global variable in a closure:

案例 1:

$closure = function() use ($global_variable) {
  // Use $global_variable to do something.
}

情况 2:

$closure = function() {
  global $global_variable; 
  // Use $global_variable to do something.
}

推荐答案

你的两个例子之间有一个重要的区别:

There is an important difference between your two examples:

$global_variable = 1;

$closure = function() use ($global_variable) {
    return $global_variable; 
};

$closure2 = function() {
    global $global_variable;
    return $global_variable;
};

$global_variable = 99;

echo $closure();    // this will show 1
echo $closure2();   // this will show 99 

use 在定义闭包时取 $global_variable 的值，而 global 取$global_variable<的当前值/code> 执行期间.

use takes the value of $global_variable during the definition of the closure while global takes the current value of $global_variable during execution.

global 从全局作用域继承变量，而 use 从父作用域继承它们.

global inherits variables from the global scope while use inherits them from the parent scope.

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