php的闭包（Closure）匿名函数详解

$a = function() use($b) {}

function callback($fun) {
$fun();
}
$msg = "Hello,everyone";
$fun = function () use($msg) {
print "This is a closure use string value,msg is: $msg. <br />/n";
};
$msg = "Hello,everybody";
callback($fun);

/**
?* 一个利用闭包的计数器产生器
?* 这里其实借鉴的是python中介绍闭包时的例子...
?* 我们可以这样考虑:
?*????? 1. counter函数每次调用,创建一个局部变量$counter,初始化为1.
?*????? 2. 然后创建一个闭包,闭包产生了对局部变量$counter的引用.
?*????? 3. 函数counter返回创建的闭包,并销毁局部变量,但此时有闭包对$counter的引用,?
?*????????? 它并不会被回收,因此,我们可以这样理解,被函数counter返回的闭包,携带了一个游离态的
?*????????? 变量.
?*????? 4. 由于每次调用counter都会创建独立的$counter和闭包,因此返回的闭包相互之间是独立的.
?*????? 5. 执行被返回的闭包,对其携带的游离态变量自增并返回,得到的便是一个计数器.
?* 结论: 此函数可以用来生成相互独立的计数器.
?*/?
function counter() {?
??? $counter = 1;?
??? return function() use(&$counter) {return $counter ++;};?
}?
$counter1 = counter();?
$counter2 = counter();?
echo "counter1: " . $counter1() . "<br />/n";?
echo "counter1: " . $counter1() . "<br />/n";?
echo "counter1: " . $counter1() . "<br />/n";?
echo "counter1: " . $counter1() . "<br />/n";?
echo "counter2: " . $counter2() . "<br />/n";?
echo "counter2: " . $counter2() . "<br />/n";?
echo "counter2: " . $counter2() . "<br />/n";?
echo "counter2: " . $counter2() . "<br />/n";?
?>

<?php
// 一个基本的购物车,包括一些已经添加的商品和每种商品的数量.
// 其中有一个办法用来计算购物车中所有商品的总价格.该办法使用了一个closure作为回调函数.
class Cart
{
??? const PRICE_BUTTER? = 1.00;
??? const PRICE_MILK??? = 3.00;
??? const PRICE_EGGS??? = 6.95;
??? protected?? $products = array();
??? public function add($product,$quantity)
??? {
??????? $this->products[$product] = $quantity;
??? }
??? public function getQuantity($product)
??? {
??????? return isset($this->products[$product]) ? $this->products[$product] :
?????????????? FALSE;
??? }
??? public function getTotal($tax)
??? {
??????? $total = 0.00;
??????? $callback =
??????????? function ($quantity,$product) use ($tax,&$total)
??????????? {
??????????????? $pricePerItem = constant(__CLASS__ . "::PRICE_" .
??????????????????? strtoupper($product));
??????????????? $total += ($pricePerItem * $quantity) * ($tax + 1.0);
??????????? };
??????? //使用用户自定义函数对数组中的每个元素做回调处理
??????? array_walk($this->products,$callback);
??????? return round($total,2);;
??? }
}
$my_cart = new Cart;
// 往购物车里添加条目
$my_cart->add('butter',1);
$my_cart->add('milk',3);
$my_cart->add('eggs',6);
// 打出出总价格,其中有 5% 的销售税.
print $my_cart->getTotal(0.05) . "n";
// The result is 54.29
?>

function html($code,$id="",$class=""){
if ($id !== "") $id = " id = "$id"" ;
$class = ($class !== "")? " class ="$class">":">";
$open = "<$code$id$class";
$close = "</$code>";
return function ($inner = "") use ($open,$close){
return "$open$inner$close";
??? };
}

<?php
$fib = function($n) use(&$fib) {
??? if($n == 0 || $n == 1) return 1;
??? return $fib($n - 1) + $fib($n - 2);
};
echo $fib(2) . "n"; // 2
$lie = $fib;
$fib = function(){die('error');};//rewrite $fib variable
echo $lie(5); // error?? because $fib is referenced by closure

<?php
$recursive = function () use (&$recursive){
// The function is now available as $recursive
}

<?php
$result = 0;
$one = function()
{
??? var_dump($result);
};
$two = function() use ($result)
{
??? var_dump($result);
};
$three = function() use (&$result)
{
??? var_dump($result);
};
$result++;
$one();??? // outputs NULL: $result is not in scope
$two();??? // outputs int(0): $result was copied
$three();??? // outputs int(1)