These examples utilize Composer's autoloader
<?php
include 'autoload.php';
$loader = new \Composer\Autoload\ClassLoader();
$loader->addPsr4('phpseclib\\', __DIR__ . '/path/to/phpseclib2.0');
$loader->register();
use phpseclib\Crypt\RSA;
use phpseclib\Net\SSH2;
$key = new RSA();
$key->loadKey(file_get_contents('private-key.txt'));
// Domain can be an IP too
$ssh = new SSH2('www.domain.tld');
if (!$ssh->login('username', $key)) {
exit('Login Failed');
}
echo $ssh->exec('pwd');
echo $ssh->exec('ls -la');