External library in CodeIgniter, with global variabele

I want to add the Mollie library (https://github.com/mollie/mollie-api-php) in my CodeIgniter project.

I have followed the steps on the github page, and since I'm not using composer I have downloaded the files and added 'require ../Molie/API/Autoloader.php' in my controller.

But with the code below, I get an error like: Undefined variable: mollie (in function ideal_get()). What I'm doing wrong?

require APPPATH.'/libraries/REST_Controller.php';
require "../Mollie/API/Autoloader.php";
class Pay extends REST_Controller {

    public $mollie;

    function __construct()
    {
        parent::__construct();
        $this->load->model('group_model');
        $this->load->model('participant_model');

        $mollie = new Mollie_API_Client;
        $mollie->setApiKey("test_jcQEp2Hkb6pBaC38GsfSPHwkcNVBGU");
    }

    function ideal_get(){
        $issuers = $mollie->issuers->all();

        $this->response($issuers, 200);
    }
}

you should put the mollie lib in your third party folder besides of that - try the following - you don't access to your mollie variable declared in your controller correctly

require APPPATH.'/libraries/REST_Controller.php';
require "../Mollie/API/Autoloader.php";
class Pay extends REST_Controller {

    public $mollie;

    function __construct()
    {
        parent::__construct();
        $this->load->model('group_model');
        $this->load->model('participant_model');

        $this->mollie = new Mollie_API_Client;
        $this->mollie->setApiKey("test_jcQEp2Hkb6pBaC38GsfSPHwkcNVBGU");
    }

    function ideal_get(){
        $issuers = $this->mollie->issuers->all();

        $this->response($issuers, 200);
    }
}