PHP迭代器 Iterator

interface Iterator extends Traversable {
　　/*获取当前元素*/
    public function current();
　　/*移动到下一个元素*/
    public function next();
　　/*获取当前元素的键值*/
    public function key();
　　/*验证当前位置是否有效*/
    public function valid();
　　/*返回到迭代器的第一个元素*/
    public function rewind();
}

<?php
class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "firstelement",
        "secondelement",
        "lastelement",
    );  

    public function __construct() {
        $this->position = 0;
    }

    function rewind() {
        var_dump(__METHOD__);
        $this->position = 0;
    }

    function current() {
        var_dump(__METHOD__);
        return $this->array[$this->position];
    }

    function key() {
        var_dump(__METHOD__);
        return $this->position;
    }

    function next() {
        var_dump(__METHOD__);
        ++$this->position;
    }

    function valid() {
        var_dump(__METHOD__);
        return isset($this->array[$this->position]);
    }
}

$it = new myIterator;

foreach($it as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}