Require_once无效(无法打开流:没有这样的文件或目录)

I have a db mysqli connection inside folder myapp/db/dbconn.php. And I'm working with file myapp/add/addcat.php. But when I put require_once 'db/dbconn.php'; it says:

Warning: require_once(../Gats/db/dbconn.php): failed to open stream: No such file or directory in C:\Program Files (x86)\Ampps\www\Gats\afegir\afegirgat.php on line 4

How can I fix this? Dbconn works for any file that isn't inside a folder (like myapp/index.php) but doesn't otherwise. Thanks in advance!

You need to require files using the relative location of them regarding your current script. So, if your folder structure is like

- Gats
  - db
    - dbconn.php
  - add
    - addcat.php

Then the proper way to require dbconn would be

require_once('../db/dbconn.php');

However, this won't scale if you have a large filebase to mantain, so I'd advise to keep entrypoints to the bare minimum and, if possible, on the root folder of your project, from which the relative route to any other file is evident.

Even better, you could have a single entrypoint, declare a constant inside it to set the BASE_PATH, and include/require everything knowing beforehand the value of BASE_PATH. (this one would need you to implement some kind of router functionality, or adopt a microframework to do that for you).