public function actionIndex(){
    $session = \YII::$app->session;
    //判断session是否开启
    if(!$session->isActive) {
      //未开启,需要开启
      $session->open();
    }
    //设置session
    $session->set('user_name','zhangsan');
    //获取session
    $user_name = $session->get('user_name');
    echo $user_name;
    //删除session
    $session->remove('user_name');
    //数组形式的session
    //设置session
    $session['userName'] = 'lisi';
    //获取session
    $user_name = $session['userName'];
    echo $user_name;
    //删除session
    unset($session['userName']);
}

public function actionIndex(){
    //设置cookie(注意这里用的是响应组件)
    $cookies = \YII::$app->response->cookies;
    $cookie_data = array('name'=>'user','value'=>'zhangsan');
    $cookies->add(new Cookie($cookie_data));
    //获取cookie(注意这里用的是请求组件)
    $cookie = \YII::$app->request->cookies;
    echo $cookie->getValue('user','default_value');//第二个参数为不存在时的默认值
    //删除cookie(注意这里用的是响应组件)
    $cookies->remove('user');
}