PHP闭包function() use()中的详细使用方法

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

}

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[php] view plain copy

<?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。

// 其中有一个方法用来计算购物车中所有商品的总价格。该方法使用了一个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);

};

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

?>

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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";};

}

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<?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

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<?php

$recursive =function ()use (&$recursive){

// The function is now available as $recursive

}

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<?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)