Estou tentando adicionar omnipay no CodeIgniter (versão 2.2.4). Segui as instruções na instalação do compositor usando este link:https://philsturgeon.uk/blog/2012/05/composer-with-codeigniter/

mas estou tendo este erro:

    Fatal error: Uncaught exception 'Omnipay\Common\Exception\RuntimeException' with message 'Class '\Omnipay\PayPal Express\Gateway' not found' in C:\xampp\htdocs\testserver\vendor\omnipay\common\src\Omnipay\Common\GatewayFactory.php:105
    Stack trace: #0 [internal function]: Omnipay\Common\GatewayFactory->create('PayPal Express')
    #1 C:\xampp\htdocs\testserver\vendor\omnipay\common\src\Omnipay\Omnipay.php(103): call_user_func_array(Array, Array)
    #2 C:\xampp\htdocs\testserver\application\controllers\Test.php(18): Omnipay\Omnipay::__callStatic('create', Array)
    #3 C:\xampp\htdocs\testserver\application\controllers\Test.php(18): Omnipay\Omnipay::create('PayPal Express')
    #4 [internal function]: Test->Pay()
    #5 C:\xampp\htdocs\testserver\system\core\CodeIgniter.php(360): call_user_func_array(Array, Array)
    #6 C:\xampp\htdocs\testserver\index.php(203): require_once('C:\xampp\htdocs...')
    #7 {main} throw,n in C:\xampp\htdocs\testserver\vendor\omnipay\common\src\Omnipay\Common\GatewayFactory.php on line 105

Eu já segui as sugestões deste post (Instalação CodeIgniter + omnipay), mas nenhuma das sugestões deles está funcionando para mim.

Estou usando o codeigniter 2.2.4 e o apache 5.4.19

Alguém pode me ajudar a resolver isso?