?php
/**
 * Created by PhpStorm.
 * Date: 2016/5/27
 * Time: 14:16
 */
namespace frontend\libs;
use Yii;
use yii\base\Action;
use yii\base\ActionFilter;
class FilterTest extends ActionFilter{
  //在action之前运行，可用来过滤输入
  public function beforeAction($action) {
    echo '在调用action前显示br/>';
    return TRUE;//如果返回值为false,则action不会运行
  }
  //在action之后运行，可用来过滤输出
  public function afterAction($action, $result) {
    return $result.'在调用action后显示br/>';//可以对action输出的$result进行过滤，retun的内容会直接显示
  }
}

?php
/**
 * Created by PhpStorm.
 * Date: 2016/5/27
 * Time: 14:19
 */
 namespace frontend\controllers;
 use yii\web\controller;
class TestbehaviorController extends Controller{
  public function behaviors(){
    return [
      'test'=>[
       'class'=>'frontend\libs\FilterTest',//调用过滤器
      ],
    ];
  }
  public function actionFilter(){
    return "当前action显示br/>";//返回的内容会递交给过滤器，由afterAction处理
  }
}