How to install and use Facebook PHP SDK without Composer - php

Question

I'm trying to embed Server Side conversion in a website (due to iOS 14 update) but I'm experiencing issues with the PHP SDK so everytime I try a conversion code in a page it turns out Fatal Error.
So my question is, how can I use/embed correctly these conversions code?
Thanks in advance to who will answer
EDIT: To explain better
I Downloaded the Facebook Php SDK from here https://php-download.com/package/facebook/php-sdk-v4 and then I uploaded in my website root, after that I've included the following code(from https://developers.facebook.com/docs/marketing-api/conversions-api/payload-helper ) in a thank you page to track "purchase" conversion:
<?php
define('SDK_DIR', __DIR__ . '/..'); // Path to the SDK directory
$loader = include SDK_DIR . '/vendor/autoload.php';
use FacebookAds\Api;
use FacebookAds\Logger\CurlLogger;
use FacebookAds\Object\ServerSide\Content;
use FacebookAds\Object\ServerSide\CustomData;
use FacebookAds\Object\ServerSide\DeliveryCategory;
use FacebookAds\Object\ServerSide\Event;
use FacebookAds\Object\ServerSide\EventRequest;
use FacebookAds\Object\ServerSide\Gender;
use FacebookAds\Object\ServerSide\UserData;
// Configuration.
// Should fill in value before running this script
$access_token = null;
$pixel_id = null;
if (is_null($access_token) || is_null($pixel_id)) {
throw new Exception(
'You must set your access token and pixel id before executing'
);
}
// Initialize
Api::init(null, null, $access_token);
$api = Api::instance();
$api->setLogger(new CurlLogger());
$events = array();
$user_data_0 = (new UserData())
->setEmail("hashed email");
$custom_data_0 = (new CustomData())
->setValue(142.52)
->setCurrency("USD");
$event_0 = (new Event())
->setEventName("Purchase")
->setEventTime(1620379012)
->setUserData($user_data_0)
->setCustomData($custom_data_0)
->setActionSource("email");
array_push($events, $event_0);
$request = (new EventRequest($pixel_id))
->setEvents($events);
$request->execute();
Of course this code do not contain token and pixel ID but in the website I filled all the variables with the right values.
I also adjusted the require on top with the right path and then i got the following error in the page:
Fatal error: Uncaught Error: Class 'FacebookAds\Api' not found in mywebsite/public_html/template/includes/analyticstracking2.inc.php:60 Stack trace: #0 /mywebsite/public_html/it/thankyou_page.php(134): require() #1 {main} thrown in mywebsite/public_html/template/includes/analyticstracking2.inc.php on line 60
On line 60 there's the following: Api::init(null, null, $access_token);
Onestly I do not understand where the issue it's coming from.
Now to answer to 'why do not use composer' I can't from a shared hosting server, if someone knows howo to do maybe I can start from there.