Problem with loading the class with php composer - php

Question

I have such a directory website:
- my application
- apps
--- Backend
--- Core
---- Core \ Config
---- Core \ Drivers (Db.php)
---- Core \ Main
--- Frontend
My composer.json file:
{
"autoload": {
"psr-4": {
"Core\\": "apps/Core/",
"Web\\": "apps/Frontend",
"Cms\\": "apps/Backend"
}
},
"require": {
"php": ">=7.0",
"phpmailer/phpmailer": "~6.0",
"monolog/monolog": "~1.23",
"mpdf/mpdf": "~7.0",
"twig/twig": "~2.5"
},
"config": {
"vendor-dir": "apps/vendor"
}
}
The moment I want to call my application \ secret \ index.php in the file:
require_once ("../apps/vendor/autoload.php");
use Core\Drivers;
use Core\Main;
$bl = new Core\Drivers\Db();
The Db.php file looks like:
namespace Core\Drivers;
class Db
{
...
}
I'm getting an error:
Fatal error: Uncaught Error: Class 'Core \ Drivers \ Db' not found in
Why?
EDIT
// autoload_psr4.php #generated by Composer
$vendorDir = dirname(dirname(__FILE__));
$baseDir = dirname(dirname($vendorDir));
return array(
'Web\\' => array($baseDir . '/apps/Frontend'),
'Twig\\' => array($vendorDir . '/twig/twig/src'),
'Symfony\\Polyfill\\Mbstring\\' => array($vendorDir . '/symfony/polyfill-mbstring'),
'Symfony\\Polyfill\\Ctype\\' => array($vendorDir . '/symfony/polyfill-ctype'),
'Psr\\Log\\' => array($vendorDir . '/psr/log/Psr/Log'),
'PHPMailer\\PHPMailer\\' => array($vendorDir . '/phpmailer/phpmailer/src'),
'Mpdf\\' => array($vendorDir . '/mpdf/mpdf/src'),
'Monolog\\' => array($vendorDir . '/monolog/monolog/src/Monolog'),
'DeepCopy\\' => array($vendorDir . '/myclabs/deep-copy/src/DeepCopy'),
'Core\\' => array($baseDir . '/apps/Core'),
'Cms\\' => array($baseDir . '/apps/Backend'),
);

Answer 1

Everything looks pretty cool but I would suggest you change the contents of secret/index.php to:
require_once __DIR__.'/../apps/vendor/autoload.php'; //A cleaner approach for requiring files
use Core\Drivers\Db; //So, you don't have to use slash when using your class in your code.
use Core\Main;
$bl = new Db();

Answer 2

use from root directory like this:
use \Core\Drivers;
use \Core\Main;
$bl = new \Core\Drivers\Db();
Use from the root directory the php will search for the given classes
in the current namespace