TP3.2で画像やファイルを一括アップロードする際の同名問題に対するPHPの解決策

<form action="{:U(&#39;Upload/index&#39;)}" enctype="multipart/form-data" method="post" >
  <p><input type="file" id="file3" name="ID[]" /></p>
  <p><input type="file" id="file4" name="ID[]" /></p>
  <input type="submit" value="上传" />
  <p><img id="img1" alt="" src="/Public/IMAGE/empty_thumb.gif" /></p>
 </form>

public function index(){
       if(!empty($_FILES)){
        $upload = new \Think\Upload();// 实例化上传类
        $upload->maxSize = 3145728;
        $upload->rootPath = './Uploads/';
        $upload->savePath = 'image/';
        //$upload->saveName = date('YmdHis').'-'.randomkeys(3);//msectime(),毫秒数13位
        $upload->saveName = 'msectime';   //自定义函数，采用13位毫秒和3位随机数
        $upload->exts   = array('jpg', 'gif', 'png', 'jpeg');
        $upload->autoSub = true;
        $upload->subName = array('date','Ymd');
        
        /* 判断$_FILES[$key]是否：一维数组，单张图片上传 -xzz0703 
         * 原理：html的input type = "file" name="IDcard"和name="IDcard[]"的区别：
         *    $_FILES前者到后台php是二维数组，后者是三维数组 
        */
        foreach($_FILES as $key=>$value){
          if(count($_FILES[$key]) == count($_FILES[$key],1)){
            $info = $upload->uploadOne($_FILES[$key]);
            if($info){
              echo json_encode(array('code'=>200,'id'=>$img_id,'name'=>$img_name));exit;
            }else{
              echo json_encode(array('code'=>0,'msg'=>$upload->getError()));exit;
            }
          }
        }
        if(count($_FILES)){
          $info = $upload->upload();//如果是二维数组，使用批量上传文件的方法
          if(!$info){
            $this->error($upload->getError());
            exit;
          }
          $img_url = '/Uploads/'.$info[0]['savepath'].$info[0]['savename'];
          $res = array('imgPath1'=>$img_url,code=>$img_url,'msg'=>$info);
          echo json_encode($res);
        }        
      }   
}

//返回当前的毫秒时间戳和随机数合并的字符串
function msectime() {
  list($msec, $sec) = explode(' ', microtime());
  $msectime = (float)sprintf('%.0f', (floatval($msec) + floatval($sec)) * 1000).randomkeys(3);
  return $msectime;
}