PHP致命错误：未找到类'Sightengine \\ SightengineClient'

after trying different ways of using the API from sightengine I can' get it to work, I followed the instructions on their site , installing via composer, but when I try to use it, I get the Class not found error in apache:

PHP Fatal error:  Uncaught Error: Class 'Sightengine\\SightengineClient' not found in /var/www/html/photobooth/app.php

PHP file:

<?php use Sightengine\SightengineClient; $client = new SightengineClient('xxxxxxx', 'xxxxxxxxx');

Missed to include the file.

When installing using composer, we have to include the file in our code

require_once 'vendor'.DIRECTORY_SEPARATOR.'autoload.php';

This will help you to include the file in code, so you can start using the class/objects