code: public function logout() 
      {
  		$auth = $this->getServiceLocator()->get('ControllerPluginManager')->get('zfcUserAuthentication');
  		
  		if($auth->hasIdentity()) {
  	        $auth->getAuthAdapter()->resetAdapters();
  	        $auth->getAuthAdapter()->logoutAdapters();
  	        $auth->getAuthService()->clearIdentity();
  		}
      }
docs: Do logout
  
  @return void