PHP迭代器的内部执行过程详解

代码如下:
class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "first_element",
        "second_element",
        "last_element",
    ); 

    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 => $value) {
 echo '输出键值：';
    var_dump($key, $value);
 //echo $key;
    echo "/n";
}

程序运行输出：
代码如下:
string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(0)
string(13) "first_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(1)
string(14) "second_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(2)
string(12) "last_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"

一般的迭代器内部需要下面的方法：
Iterator::current — Return the current element 返回当前元素
Iterator::key — Return the key of the current element 返回当前元素的键
Iterator::next — Move forward to next element 移向下一个元素
Iterator::rewind — Rewind the Iterator to the first element 重新回到第一个元素
Iterator::valid — Checks if current position is valid 检查当前位置的有效性
如果不是很清楚迭代器的内容工作流程，可以查看下面的迭代器对数组的遍历过程：