匿名函數(shù)
匿名函數(shù)(Anonymous function),也叫閉包函數(shù)(closures),允許臨時(shí)創(chuàng)建一個(gè)沒(méi)有指定名稱(chēng)的函數(shù),最經(jīng)常用作回調(diào)函數(shù)(callback)參數(shù)的值。
匿名函數(shù)的實(shí)現(xiàn)
匿名函數(shù)是目前是通過(guò)Closure類(lèi)來(lái)實(shí)現(xiàn),匿名函數(shù)會(huì)產(chǎn)生這個(gè)類(lèi)的對(duì)象。自PHP 5.4起,這個(gè)類(lèi)帶有一些方法,允許在匿名函數(shù)創(chuàng)建后對(duì)其進(jìn)行更多的控制。
注意:PHP手冊(cè)特別說(shuō)明__invoke()這個(gè)魔術(shù)方法與匿名函數(shù)的實(shí)現(xiàn)過(guò)程無(wú)關(guān)。
Closure類(lèi)如下:
Closure { /* 方法 */ __construct ( void ) public static Closure bind ( Closure $closure , object $newthis [, mixed $newscope = 'static' ] ) public Closure bindTo ( object $newthis [, mixed $newscope = 'static' ] ) }Closure::__construct — 用于禁止實(shí)例化的構(gòu)造函數(shù)Closure::bind — 復(fù)制一個(gè)閉包,綁定指定的$this對(duì)象和類(lèi)作用域。Closure::bindTo — 復(fù)制當(dāng)前閉包對(duì)象,綁定指定的$this對(duì)象和類(lèi)作用域。
匿名函數(shù)例子:
$func = function($str){ echo $str;};$func('hello');
閉包
閉包是指在創(chuàng)建時(shí)封裝周?chē)鸂顟B(tài)(如變量)的函數(shù),即使閉包所在的環(huán)境的不存在了,閉包中封裝的狀態(tài)依然存在。
閉包的實(shí)現(xiàn)
將匿名函數(shù)放在一個(gè)普通函數(shù)中(也可以將匿名函數(shù)返回),就構(gòu)成了一個(gè)閉包。
function closureFunc(){ $func = function(){ echo 'hello'; } $func();}closureFunc();//輸出:hello
閉包的使用
在匿名函數(shù)中引入局部變量時(shí)需要用到use
關(guān)鍵字。這是因?yàn)镻HP中的變量范圍只在它的生效范圍中。在匿名函數(shù)里并沒(méi)有對(duì)變量進(jìn)行定義,所以需要使用use
關(guān)鍵字
function closureFunc1(){ $num = 1; $func = function() use($num){ echo $num; }; $func();}closureFunc2();//輸出
閉包返回匿名函數(shù)并傳參
function closureFunc2(){ $num = 1; $func = function($str) use($num){ echo $num; echo $str; }; return $func;}$func = $closureFunc2();$func('hello');//輸出 1 hello
以上,歡迎討論~
把閉包簡(jiǎn)單理解成“定義在一個(gè)函數(shù)內(nèi)部的函數(shù)”。
所以,在本質(zhì)上,閉包就是將函數(shù)內(nèi)部和函數(shù)外部連接起來(lái)的一座橋梁。
四、閉包的用途
閉包可以用在許多地方。它的最大用處有兩個(gè),一個(gè)是前面提到的可以讀取函數(shù)內(nèi)部的變量,另一個(gè)就是讓這些變量的值始終保持在內(nèi)存中。

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