The below code is an example only.  Tested with PHP 7.3 and Guzzle 6.5.2


<?php
require __DIR__ . '/vendor/autoload.php';

use GuzzleHttp\Client;

$client = new Client();

$method = 'socks5h';
$username = 'someUsername';
$password = 'somePassword';
$proxyServer = 'ca-1.us.proxies.com';
$proxyPort = 35000;

$proxy = $method.'://'.$username.':'.$password.'@'.$proxyServer.':'.$proxyPort;

$site = 'https://api.ipify.org';

try {
    $res = $client->request('GET', $site, ['proxy' => $proxy]);
    $response = $res->getBody();
} catch (\Exception $e) {
    die($e);
}