可在内部迭代自己的外部迭代器或类的接口。
接口摘要
Iterator extends Traversable { /* 方法 */ abstract public mixed current ( void ) abstract public scalar key ( void ) abstract public void next ( void ) abstract public void rewind ( void ) abstract public boolean valid ( void ) }
预定义迭代器
PHP 已经提供了一些用于日常任务的迭代器,如SPL迭代器。
范例
Example #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; } 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"; } ?>
以上例程的输出类似于:
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"
方法列表
Iterator::current — 返回当前元素
Iterator::key — 返回当前元素的键
Iterator::next — 向前移动到下一个元素
Iterator::rewind — 返回到迭代器的第一个元素
Iterator::valid — 检查当前位置是否有效