在某些对象上调用时重载count()的行为 [英] Overload the behavior of count() when called on certain objects

问题描述

可能重复:
使用count()实现ArrayAccess的对象的count元素?

Possible Duplicate:
Count elements for objects implementing ArrayAccess using count()?

在PHP 5中，您可以使用魔术方法，重载某些类等.在C ++中，只要参数类型不同，就可以实现存在的函数.有没有办法在PHP中做到这一点?

In PHP 5, you can use magic methods, overload some classes, etc. In C++, you can implement functions that exist as long as the argument types are different. Is there a way to do this in PHP?

我想做的一个例子是:

class a {
    function a() {
        $this->list = array("1", "2");
    }
}

$blah = new a();

count($blah);

我想返回2.IE计算类中特定数组的值.因此，在C ++中，我执行此操作的方式可能如下所示:

I would like blah to return 2. IE count the values of a specific array in the class. So in C++, the way I would do this might look like this:

int count(a varName) { return count(varName->list); }

基本上，我正在尝试简化大型应用程序的数据调用，因此我可以调用它:

Basically, I am trying to simplify data calls for a large application so I can call do this:

count($object);

而不是

count($object->list);

该列表将可能是对象列表，因此，取决于使用方式，如果有人必须以当前方式进行操作，这可能真是令人讨厌的声明:

The list is going to be potentially a list of objects so depending on how it's used, it could be really nasty statement if someone has to do it the current way:

count($object->list[0]->list[0]->list);

所以，我可以做些类似的事情吗

So, can I make something similar to this:

function count(a $object) {
    count($object->list);
}

我知道PHP的计数接受混合的var，所以我不知道是否可以覆盖单个类型.

I know PHP's count accepts a mixed var, so I don't know if I can override an individual type.

推荐答案

听起来您想实现 Countable 接口:

It sounds like you want to implement the Countable interface:

class a implements Countable {
    public function __construct() {
        $this->list = array("1", "2");
    }

    public function count() {
      return count($this->list);
    }
}

$blah = new a();

echo count($blah); // 2

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