<?php

/*
 * Iterater 简单模式
 */
class sample  implements Iterator
{
    private $_items ;
 
    public function __construct(&$data) {
        $this->_items = $data;
    }
    public function current() {  //当前值
        return current($this->_items);
    }
 
    public function next() {    //移动指针到下一位
        next($this->_items);   
    }
 
    public function key() {    //当前键
        return key($this->_items);
    }
 
    public function rewind() {  //初始化指针
        reset($this->_items);
    }
 
    public function valid() {                                                                              
        return ($this->current() !== FALSE);
    }
}

/** DEMO */
$data = array(1,'kiy'=>1, 2, 3, 4, 5);
$sa = new sample($data);
echo 'curr'. $sa->current() .'<br/>';
print_r($sa->key()); echo  '<br/>';
 $sa->rewind();
print_r($sa->valid()); echo  'valid<br/>';
foreach ($sa AS $key => $row) {
    echo $key, ' ', $row, '<br />';
}
/*

 * 文件迭代器

 */

class RecursiveFileFilterIterator extends FilterIterator
{
    // 满足条件的扩展名
    protected $ext = array('jpg','gif');

    /**
     * 提供 $path 并生成对应的目录迭代器
     */
    public function __construct($path)
    {
        parent::__construct(new RecursiveIteratorIterator(new RecursiveDirectoryIterator($path)));
    }

    /**
     * 检查文件扩展名是否满足条件
     */
    public function accept()
    {
        $item = $this->getInnerIterator();
        if ($item->isFile() && in_array(pathinfo($item->getFilename(), PATHINFO_EXTENSION), $this->ext))
        {
            return TRUE;
        }
    }
}

// 实例化
foreach (new RecursiveFileFilterIterator('D:/') as $item)
{
    echo $item . PHP_EOL;
}