<form action="提交到处理地址" method="post" enctype="multipart/form-data" class="form-horizontal">

      <div class="form-group">

              <label class="col-lg-2 col-sm-2 control-label">上传图片</label>

              <div class="col-lg-4">

                     <input type="file" name="photo">

              </div>

      </div>

      <div class="form-group">

              <div class="col-lg-offset-2 col-lg-4">

                      <button type="submit" name="submit" class="btn btn-default">确定</button>

              </div>

       </div>

</form>

public function imgApp(){

        //方式一：电脑上传文件

        $image = $_FILES["photo"]["tmp_name"];

        $fp = fopen($image, "r");

        $file = fread($fp, $_FILES["photo"]["size"]); //二进制数据流

        //保存地址

        $imgDir = './Uploads/';   //必须是项目所在的绝对路径

        //要生成的图片名字

        $filename = date("Ym")."/".md5(time().mt_rand(10, 99)).".png"; //新图片名称

        $newFilePath = $imgDir.$filename;

        $data = $file;

        $newFile = fopen($newFilePath,"w"); //打开文件准备写入

        fwrite($newFile,$data); //写入二进制流到文件

        fclose($newFile); //关闭文件

        //写入数据库

        $arr = array(

                "uid" => 1, //用户id

                "cid" => 1, //分类id

                "a_title" => $_POST["a_title"], //标题

                "a_content" => $_POST["a_content"], //内容

                "photo" => $filename, //图片路径

                "a_urgent" => $_POST['status'] == 'on' ? 0 : 1, //是否急需

                "add_time" => time(), //创建时间

            );

        if(empty($arr["a_title"])){

            $this->error("标题不为空");

        } else if(empty($arr["a_content"])) {

            $this->error("内容不为空");

        }

        if($db = M("answer")->add($arr)){

            $this->success("保存成功", "demo2");

        } else {

            $this->error("失败");

        }

}