# OuterIterator # [The Countable interface](https://www.php.net/manual/zh/class.countable.php#class.countable) > 类实现**Countable**可被用于[count()](https://www.php.net/manual/zh/function.count.php)函数. > 实现它的类可以用count函数来统计此类的属性 ## 接口摘要 ``` <pre class="calibre17">``` Countable <span class="token3">{</span> <span class="token">/* 方法 */</span> abstract public count <span class="token3">(</span> void <span class="token3">)</span> <span class="token3">:</span> int <span class="token">//统计一个对象的元素个数</span> <span class="token3">}</span> ``` ```