Why doesn't php find the package from composer?

Question

Composer

project structure:
user
-data
--coposer.json
--www
---site.ru
----index.php
there were no errors during installation, I use composer for the first time

Answer 1

First, install the composer in the folder with the site, otherwise you have everything scattered incomprehensibly how. In index.php, include the file from the vendor folder and don't forget to include the classes via use