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

<?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 = [];

    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
?>

<?php

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)