Zend_Http_Client::setAuth PHP Method

    public function setAuth($user, $password = '', $type = self::AUTH_BASIC)
    {
        // If we got false or null, disable authentication
        if ($user === false || $user === null) {
            $this->auth = null;
            // Clear the auth information in the uri instance as well
            if ($this->uri instanceof Zend_Uri_Http) {
                $this->getUri()->setUsername('');
                $this->getUri()->setPassword('');
            }
            // Else, set up authentication
        } else {
            // Check we got a proper authentication type
            if (!defined('self::AUTH_' . strtoupper($type))) {
                /** @see Zend_Http_Client_Exception */
                require_once 'Zend/Http/Client/Exception.php';
                throw new Zend_Http_Client_Exception("Invalid or not supported authentication type: '{$type}'");
            }
            $this->auth = array('user' => (string) $user, 'password' => (string) $password, 'type' => $type);
        }
        return $this;
    }

 public function __construct($apiKey, $subdomain, Zend_Http_Client $client)
 {
     $this->apiKey = $apiKey;
     $this->client = $client;
     $this->subdomain = $subdomain;
     $this->client->setAuth($this->apiKey, 'X');
 }