Why doesn't Composer see the namespace?

Question

Composer

Good afternoon, there is a project where you need to use Ratchet (php library for web sockets). It is downloaded via composer, I have never used it before, that's the problem. I can not understand why the namespace is not visible from another file. Here is the structure:

Composer.json:

{
   "autoload": {
        "psr-4": {
            "App\\": "src",
        }
    }
   ...
}

In chat.php

namespace App;
class Chat implements MessageComponentInterface { ...
}

In server.php

use App\Chat;
$chat =  new Chat();

And an error occurs when starting server.php (here is only the main one, so the lines in the error are different)

Fatal error: Uncaught Error: Class 'App\Chat' not found in D:\P\Xampp\htdocs\chat\server\src\server.php:10 Stack trace: #0 {main} thrown in D:\P\Xampp\htdocs\chat\server\src\server.php on line 10

Roughly speaking, for some reason, the class from chat.php is not visible in server.php. I didn’t write much in php before, but I seemed to be doing everything right, people are still the same. If anyone knows what the problem is, please help.

Answer 1

PSR-4

"psr-4": {
    "App\\": "src/"
}

And capitalized class file names (Chat.php, Server.php)