网站根目录extend/function.php文件内写入

if (!function_exists('diy_getArcrank')){
   //显示文档的会员阅读权限名称
   function diy_getArcrank($arcrank = '')
   {
       static $users_level_list = [];
       if (empty($users_level_list)) {
          $users_level_list = \think\Db::name('users_level')->field('level_name,level_value')
             ->where('lang', get_current_lang())
             ->order('is_system desc, level_value asc')
             ->getAllWithIndex('level_value');
       }
       if (!empty($users_level_list[$arcrank])) {
          return $users_level_list[$arcrank]['level_name'];
       } else if (empty($arcrank)) {
          $firstUserLevel = current($users_level_list);
          return $firstUserLevel['level_name'];
       } else {
       return '';
       }
    }
}