//递归
function readDirDeep($path,$deep = 0)
{
    $handle = opendir($path);
    while(false !== ($filename = readdir($handle))){
        if($filename == '.' || $filename == '..') continue;
        echo str_repeat('&nbsp;',$deep*5) . $filename.'<br>';
            //str_repeat(str,n) 重复一个str字符串n次
        if(is_dir($path.'/'.$filename)){
            readDirDeep($path.'/'.$filename,$deep+1);
            }
        }
        //闭关
        closedir($handle);
}

//队列
队列的方式就是遇到目录就放入队列,非目录打印就好
function readDirQueue($dir)
{
    $dirs = [$dir];

    while ($path = array_shift($dirs)) {
        if (is_dir($path) && $handle = opendir($path)) {
            while (false !== ($filename = readdir($handle))) {
                if ($filename == '.' || $filename == '..') continue;
                $real_path = $path . DIRECTORY_SEPARATOR . $filename;

                if(is_dir($real_path)) {
                    $dirs[] = $real_path;
                }else {
                    echo $real_path . '<br/>';
                }
            }
            //闭关
            closedir($handle);
        }
    }

}