1、理解闭包之前先知道一个PHP的array_walk函数
<?phpfunction myfunction($value,$key){echo "The key $key has the value $value<br>";}$a=array("a"=>"red","b"=>"green","c"=>"blue");array_walk($a,"myfunction");?>结果是：（调用了3次myfunction函数）The key a has the value redThe key b has the value greenThe key c has the value blue<?phpclass Cart ?{ ?????const PRICE_BUTTER ?= 1.00; ?????const PRICE_MILK ???= 3.00; ?????const PRICE_EGGS ???= 6.95; ????????protected ??$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($product)); ?????????????????//其中constant 返回 上边定义常量的值 ??????????????//跟self::访问一样，self不能再这里使用，所以用上边 ???????????????$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 ??> ???
&符号则使用变量的地址（传址）
PHP闭包
原文地址：https://www.cnblogs.com/aoxueshou/p/9547330.html