Question about work - COMPOSER - autoload?

Question

Composer

I have a question.
In the localhost folder I have an index.php file and a php_classes folder in which I created 2 test classes.
Then I install via composer console to this localhost folder. And I create a file autoload. When I display classes in index.php, they are loaded, all the rules work.
The root folder of the site is localhost.
And if I do this, for example, in the localhost folder I create the APP folder and then in this folder I create the index.php file, the php_classes folder and HERE I install composer, then when I want to display the classes, an
error occurs - Fatal error: Uncaught Error: Class 'php_classes\Worker' not found in C:\OSPanel\domains\localhost\app\index.php
Why is this happening where is my mistake?

Answer 1

established practice (names other than the vendor are conditional)
app - current project
public - www root
src - for libs that are planned to be used in other
vendors in the future
composer.json
How to describe your lib in the simplest version
of "autoload": {
"psr-4" : {
"antson\\": "src/antson/"
}
},
in src create folder antson (who is the author), subfolder mylib in it
and
then MySuperPuper.php
<?php
namespace antson\mylib;
class MySuperPuper{
....
}
in the main project
$a = new antson\mylib\MySuperPuper();
or
use antson\mylib\MySuperPuper;
...
$a = MySuperPuper();
This is greatly simplified! We carefully read about PSR and namespace.