文件上传显示非法上传文件！
html代码：
<form action="__URL__/up" enctype="multipart/form-data" method="post" >
<input type="text" name="name" />
<input type="file" name="photo" />
<input type="submit" value="提交" >
</form>
php代码：
public function up(){

$upload = new \Think\Upload();// 实例化上传类

$upload->maxSize = 3145728 ;// 设置附件上传大小
$upload->exts = array('jpg', 'gif', 'png', 'jpeg');// 设置附件上传类型
$upload->rootPath = './Public/'; // 设置附件上传根目录
$upload->savePath = ''; // 设置附件上传（子）目录
// 上传文件
$info = $upload->upload($_FILES['photo']);
echo $upload->getError();


$this->display();
}