在php中的require_once上没有这样的文件或目录错误

I am trying to make a login system for my app, and needed to use php for it. However I'm really new to php so I got errors. First of all, I am using a free web hosting for now, so it might be the issue here. That being said, here is the error part of my php:

<?php
require_once 'include/DB_Functions.php';
?>

And it gives me this error:

Warning: require_once(include/DB_Functions.php): failed to open stream: No such file or directory in /srv/disk3/1965965/www/yigittest.atwebpages.com/login.php on line 2

Fatal error: require_once(): Failed opening required 'include/DB_Functions.php' (include_path='.:/usr/local/php-5.4.45/share/pear') in /srv/disk3/1965965/www/yigittest.atwebpages.com/login.php on line 2

However, my include folder contains all the required php files. So what might be the issue here?

Try this demo code or plz share your folder structure

require_once(__DIR__.'/../include/DB_Functions.php');