php 500 Namespace declaration statement has to be the very first statement or after any declare call in the script

Namespace declaration statement has to be the very first statement or after any declare call in the script

<?php

namespace app\admin\controller;
use think\facade\View;
use think\facade\Lang;
use think\captcha\facade\Captcha;

原因是编码问题

格式应该选择UTF-8无BOM型