<?php  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:/history') as $item) {      echo $item . PHP_EOL;  }