How to get the first-level directory of a file in php (pure code)

// 获取目录一层的方法
/*
   *  @param  readfileone //读取一层文件夹内容
   *  @param  dir  // 查找的路径
   *  @param
   *  @param
   */
function   readfileone($dirName){
    $array=array();
    $dir='./Public/Uploads/'.$dirName;
    if(is_dir(iconv('utf-8','gb2312',$dir))==true){
        if($handle=opendir(iconv('utf-8','gb2312',$dir))){
            while(false!==($files=readdir($handle))){
                $files=iconv('gb2312','utf-8',$files);
                if($files!="."&&$files!=".."){
                    $files=iconv('utf-8','utf-8',$files);
                    $dir=iconv('utf-8','utf-8',$dir);
                    if(is_dir($dir."/".$files))
                    {
                        $new_dir=$dir."/".$files;
                        readfileone($new_dir);
                    }
                    else
                    {
                        $str=$dir."/".$files;
                        $str=iconv('utf-8','utf-8',$str);
                        // session('success.file',$str);
                        array_push($array,$str);
                    }
                }
            }
        }
        closeDir($handle);
    }else{
        //  echo '没有找到目录';
        array_push($array,'没有找到目录');
        array_push($array,'fail');
    }
    return $array;//返回二维数组
}