Symfony 4 controllers in sub folders producing error - symfony

Question

Just a quick question as to why I'm getting this
The autoloader expected class "App\Controller\Admin\AdminUnitController" to be defined in file "/home/glen/public_html/businessdirectory.glendev.local/vendor/composer/../../src/Controller/Admin/AdminUnitController.php". The file was found but the class was not in it, the class name or namespace probably has a typo in /home/glen/public_html/businessdirectory.glendev.local/config/services.yaml (which is loaded in resource "/home/glen/public_html/businessdirectory.glendev.local/config/services.yaml").
I have AdminUnitController.php with class name AdminUnitController. All was well until I decided I want the admin controllers in their own sub folder like this:
Controller\Admin\AdminUnitController.php

Answer 1

From the autoloader message, your issue is quite clear, your file is indeed where it should be but your class or namespace is wrong.
I would guess you changed the file structure but did not adapt your namespace.
Given the file src\Controller\Admin\AdminUnitController.php
Your class should look like this (pay specific attention at the namespace):
<?php
namespace App\Controller\Admin;
class AdminUnitController
{
// some code here
}
That is actually not a Symfony behavior you are facing here, but one of composer, that serves Symfony with the autoloader and that uses PSR-4 class autoloading convention.
For Reference
1) see your composer.json that have those lines:
{
// some definitions here
"autoload": {
"psr-4": {
"App\\": "src/"
}
},
"autoload-dev": {
"psr-4": {
"App\\Tests\\": "tests/"
}
},
// some more definitions here
}
2) see the PSR-4 naming convention: and especially the examples in their documentation: https://www.php-fig.org/psr/psr-4/#3-examples