Composer introduces a third-party class library, and introduces composer's autoload.php in the entry file to automatically load the file

The project has an entry file, just require it in the entry file

First require the third-party class library, and then use it. Then you can instantiate this class, for example:

<?php
namespace common\services\money;

require_once ROOT_PATH . '/extensions/payssion/lib/PayssionClient.php';

use PayssionClient;

class PayssionService
{
    public function test()
    {
        $payssion = new PayssionClient();
    }
}