Iterator（迭代器）接口

(PHP 5, PHP 7, PHP 8)

简介

可在内部迭代自己的外部迭代器或类的接口。

接口摘要

interface Iterator extends Traversable {
/* 方法 */
public function current(): mixed
public function key(): mixed
public function next(): void
public function rewind(): void
public function valid(): bool
}

预定义迭代器

PHP 已经提供了一些用于日常任务的迭代器。 详细列表参见 SPL 迭代器。

示例

示例 #1 基本用法

这个例子展示了使用 foreach 时，迭代器方法的调用顺序。 

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

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

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

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

    #[\ReturnTypeWillChange]
    public function key() {
        var_dump(__METHOD__);
        return $this->position;
    }

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

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

$it = new myIterator;

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

以上示例的输出类似于：

string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(0)
string(12) "firstelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(1)
string(13) "secondelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(2)
string(11) "lastelement"

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

参见

参见 遍历对象。

目录