php jQuery.form.js插件 无刷新上传图片

php
/*上传图片方法*/
$type = isset($_REQUEST['type']) ?  $_REQUEST['type'] : ''; //上传图片
if($action=='upload' && $type == 'img'){
    if ($_FILES["timg"]["error"] > 0)
    {
        echo "error";
    }
    else
    {
        $type = $_FILES["timg"]["type"];
        $type = explode('/',$type);
        if($type[0] == 'image')
        {
            $dirname = 'images/upload/'.date('md');
            $imgname = date('YmdHis').'.jpg';
            if(!file_exists($dirname)){
                mkdir($dirname,0777,true);//创建目录
            }
            move_uploaded_file($_FILES["timg"]["tmp_name"],
                $dirname.'/' . $imgname);
            $path = $dirname.$imgname;
            echo 'success';
        }
        else
        {
            echo 'error';
        }
    }

}


html

!--jquery.form.js-->
<script language="javascript" type="application/javascript" src="js/jquery.form.js">
</script>


<!--表单提交-->
<script>
   $(function ()
   {

      <!--jquery.form.js上传图片按钮-->
      var ajaxFormOption = {
         success: function (result) { //提交成功的回调函数
            alert(result);
         }
      };
      $("#upload_button").click(function () {
         $("#upload_form").ajaxSubmit(ajaxFormOption);
      });

</script>

<form action="cishan.php?action=upload&type=img" method="post" id="upload_form" enctype="multipart/form-data" >
<input type="file" id="timg" name="timg"><input type="button" id="upload_button" value="上传">
</form>