在Codeigniter控制器中使用ZendAMF

Not sure if I am going the best way about this, I am trying to implement ZENDAMF with codeigniter. One of the problems I have had is that I want to be able to check if the user is logged in before allowing them to make any requests to the servrices behind the zendamf gateway. I did ask a previous question about how to get it to do the check in the construct, but I found out that was not possible.

My next line of thought was to create the gateway as a controller that way I would be able to access my authentication library before the request was posted to the zend amf server. But when I make a call to the service is is not recognizing any of the CodeIgniter methods.

at the moment I am not doing the logged in check as I want to get the amf server working first, so the example I have choosen is to try and return my UserDetails.

here is my gateway.php controller

<?php
// Set up debug
class Gateway extends CI_Controller
{


    function __construct()
    {
        parent::__construct();

        error_reporting(E_ALL | E_STRICT);
        ini_set("display_errors", "on");


        ini_set("include_path",
        ini_get('include_path') . ':'
                        . '/Applications/MAMP/htdocs/app/application/libraries/');
        require_once("Zend/Amf/Server.php");
        // Start Server
        $server = new Zend_Amf_Server();

        // Zend_Amf_Server require.
        // Require the ZendAmfServiceBrowser class
        require_once("Zend/browser/ZendAmfServiceBrowser.php");
        // Class requires.
        require_once("services/Testservice.php");
        //require_once( "services/ReturnTests.php" ); 

        // Register Demo Classes
        $server->setClass("Testservice");
        //$server->setClass( "ReturnTests" );
        //$server->setResponse('test');
        // Add the ZamfBrowser service class so ZamfBrowser can retrieve method information.
        $server->setClass("ZendAmfServiceBrowser");
        // Set a reference to the Zend_Amf_Server object so ZendAmfServiceBrowser class can retrieve method information.
        ZendAmfServiceBrowser::$ZEND_AMF_SERVER = $server;
         $server->setProduction(false);

        // Handle ZendAMF request
        echo ($server->handle());
         redirect(base_url().'Gateway');

    }
}

and this is my testservice

<?php

class Testservice extends CI_Controller
{
    function __construct()
    {
        parent::__construct();
    }

function UserDetails()
    {
        $this->load->model('users_model');

        // Grab user info
        $user_id = 3;//$this->session->userdata('user_id');
        $this->user = $this->users_model->get_user_by_id($user_id);
        $this->data['user'] = $this->user;

        return $this->data;
    }
}

when I implement all of this I get the following response:

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message:  Undefined property: Testservice::$users_model</p>
<p>Filename: services/Testservice.php</p>
<p>Line Number: 90</p>

If I am extending CI_Controller I would have though that it should allow me to access all my models.

Any ideas I am really stumped on this now.

Thanks In Advance