Table of Contents
匿名函数的实现
闭包的实现
闭包的使用
Home php教程 php手册 PHP匿名函数和闭包的总结

PHP匿名函数和闭包的总结

May 29, 2018 pm 04:09 PM
php anonymous function Closure

匿名函数

匿名函数(Anonymous function),也叫闭包函数(closures),允许临时创建一个没有指定名称的函数,最经常用作回调函数(callback)参数的值。

匿名函数的实现

匿名函数是目前是通过Closure类来实现,匿名函数会产生这个类的对象。自PHP 5.4起,这个类带有一些方法,允许在匿名函数创建后对其进行更多的控制。

注意:PHP手册特别说明__invoke()这个魔术方法与匿名函数的实现过程无关。

Closure类如下:

Closure {
    /* 方法 */
    __construct ( void )
    public static Closure bind ( Closure $closure , object $newthis [, mixed $newscope = 'static' ] )
    public Closure bindTo ( object $newthis [, mixed $newscope = 'static' ] )
    }Closure::__construct — 用于禁止实例化的构造函数Closure::bind — 复制一个闭包,绑定指定的$this对象和类作用域。Closure::bindTo — 复制当前闭包对象,绑定指定的$this对象和类作用域。
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匿名函数例子:

$func = function($str){
    echo $str;};$func('hello');
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闭包

闭包是指在创建时封装周围状态(如变量)的函数,即使闭包所在的环境的不存在了,闭包中封装的状态依然存在。

闭包的实现

将匿名函数放在一个普通函数中(也可以将匿名函数返回),就构成了一个闭包

function closureFunc(){
    $func = function(){
        echo 'hello';
    }
    $func();}closureFunc();//输出:hello
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闭包的使用

在匿名函数中引入局部变量时需要用到use关键字。这是因为PHP中的变量范围只在它的生效范围中。在匿名函数里并没有对变量进行定义,所以需要使用use关键字

function closureFunc1(){
    $num = 1;
    $func = function() use($num){
        echo $num;
    };
    $func();}closureFunc2();//输出
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闭包返回匿名函数并传参

function closureFunc2(){
    $num = 1;
    $func = function($str) use($num){
        echo $num;
        echo $str;
    };
    return $func;}$func = $closureFunc2();$func('hello');//输出 1 hello
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以上,欢迎讨论~

把闭包简单理解成“定义在一个函数内部的函数”
所以,在本质上,闭包就是将函数内部和函数外部连接起来的一座桥梁。

四、闭包的用途
闭包可以用在许多地方。它的最大用处有两个,一个是前面提到的可以读取函数内部的变量,另一个就是让这些变量的值始终保持在内存中

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