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)沒有指定名稱的函數(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Closure類來實(shí)現(xiàn)，匿名函數(shù)會(huì)產(chǎn)生這個(gè)類的對(duì)象。自PHP 5.4起，這個(gè)類帶有一些方法，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)特別說明__invoke()這個(gè)魔術(shù)方法與匿名函數(shù)的實(shí)現(xiàn)過程無關(guān)。
Closure類如下：
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)封裝周圍狀態(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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