Composer PSR-0 autoloading dont work - php

Question

I have problem with autoloading module controller class from my app. I try to configure composer.json but still not working. Probably am doing somthing wrong with this directory structure. I try examples from composer doc but again dont work...
Directory structure:
|- admin
|----- modules
|--------- Menu
|------------Controller
|--------------MenuController.php
Lets see composer.json
{
"autoload": {
"psr-0": { "Admin\\Modules\\": "" }
}
}
I try to set path but nothing again // "Admin\Modules\": "admin/modules"
Menu controller:
namespace Admin\Modules\Menu\Controller;
class MenuController extends AbstractAdminBaseController
FrontController
require 'vendor/autoload.php';
new \Admin\Modules\Menu\Controller\MenuController();
All time Class not found. I try 100 examples from google and nothing. Any example how to slowe this problem? Thanks
Update structure:
├───admin
│ └───modules
│ └───Menu
│ └───controller
│ └───MenuController.php
├───vednor
│ └───autoload.php
│ └───composer
│ └───autoload_classmap.php
│ └───autoload_namespaces.php
│ └───autoload_psr4.php
│ └───autoload_real.php
│ └───ClassLoader.php
├───public
├───assets
├───index.php
├───composer.json
├───composer.lock

Answer 1

Your PSR-0 will never work, because this standard dictates that the path to the file has to be EXACTLY like the classname. Note that your first part of the namespace is "Admin", but the first directory part is only "admin" - cases must match exactly, or it won't work (or will only work with case insensitive filesystems).
You will succeed with using PSR-4, though. Why? Because with PSR-4, the given namespace prefix is removed from the full classname, and the rest is being converted into a path that is searched in the directory given for the namespace prefix.
Example for your case:
"autoload": {
"psr-0": { "Admin\\Modules\\": "" }
}
Will not work because the files are in path admin/modules, but must be in Admin/Modules.
"autoload": {
"psr-4": { "Admin\\Modules\\": "admin/modules/" }
}
Will work because the prefix Admin\Modules\ is removed and the remaining class name is being converted to a path and added to admin/modules.
Ah, one gotcha! It will NOT work, because you chose to name the class ...\Controller\..., but the path once again .../controller/....
Honestly, I'd highly recommend to convert your file names and location to PSR-4 compatibility, even for the prefixed directories that you'd be able to work around with Composer. This will eliminate the surprising lowercase directory structures I see.
I mean: Why is that controller directory even lower case in the first place if every class located there is Controller? I really can't understand this.