PHP - 'use()'或'global'之间的区别,用于访问闭包中的全局变量？

Question

以下两种在闭包中访问全局变量的情况之间是否存在任何性能或其他差异:

情况1:

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

案例2:

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

Answer 1

您的两个示例之间存在重要差异:

$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获取$global_variable闭包定义期间的值,同时global获取$global_variable执行期间的当前值.

globaluse从父作用域继承变量时从全局作用域继承变量.