Facebook SDK

Controller

public function someAction()
{
    $facebook = $this->getServiceLocator()->get('Facebook');
}

Module.php

    public function getServiceConfig()
    {
        return array(
            'factories' => array(
                'Facebook' => function($sm) {
                    $config = $sm->get('Config');
                    $facebookConfig = isset($config['facebook']) ? $config['facebook'] : array();

                    return new Facebook($facebookConfig);
                },
        );
    }