Jquery+PHP怎样实现文件批量上传?

如题.
我现在代码是这样的:
index.html文件里:
<div id="upload_area">
<form action="upload_page.php" method="post" enctype="multipart/form-data" name="upload">
<input type="file" name="files" ><input type="button" value="添加" name="add" id="add">
<input type="submit" name="sub" value="上传">
<input type="hidden" value="<?php echo 'date(Y-m-d)';?>">
</form>
</div>
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upload_page.php文件里:
$time=$_POST['time'];
$name=explode('.',$_FILES['files']['name']);
$ext=$name[count($name)-1];
//获取后缀名;
if($_FILES['files']['name']==''){echo "<script>alert('请选择上传文件');location.href='upload.php'</script>";}
else{
if(is_uploaded_file($_FILES['files']['tmp_name'])){
if(!@move_uploaded_file($_FILES['files']['tmp_name'],'upload/'.$user.$time.'.'.$ext)){
echo "<script>alert('移动失败');history.back();</script>";
}
}else{echo "<script>alert('找不到文件');history.back();</script>";
            }
mysql_query("INSERT INTO 表(username,time,geshi,kemu) VALUES ('$user','$time','$ext')");
echo "<script>alert('上传成功');location.href='upload.php'</script>";}
?>
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我现在是想实现,当我点添加按钮的时候.用Jquery增加一个文件域.点击删除就删除一个文件域.
主要是要实现文件批量上传这个功能;
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求大神指点