example.php

<?php
spl_autoload_register(function ($classname)
{
    $dirs = ['./twig-3.4.3/'];
    foreach ($dirs as $dir) {
        $filename = $dir . str_replace('\\', '/', $classname) .'.php';
        if (file_exists($filename)) {
            require_once $filename;
            break;
        }
    }
});

$loader = new \Twig\Loader\FilesystemLoader('templates');
$twig = new \Twig\Environment($loader, [
    'cache' => 'cache',
]);

print $twig->render('index.html', ['name' => 'Max']);