class Article extends \yii\db\ActiveRecord 
{ 
  //这里声明被关联字段 
  public $class_name; 
   
  /** 
   * @inheritdoc 
   */ 
  public static function tableName() 
  { 
    return '{{%article}}'; 
  } 
  ... 
 //关联 mysite_article_class 表 
  public function getArticleClass(){ 
    /** 
    * 第一个参数为要关联的子表模型类名称， 
    * 第二个参数指定通过子表的 id 去关联主表的 article_class 字段 
    */ 
    return $this->hasMany(ArticleClass::className(), ['id' => 'article_class']); 
  }  
   
} 

public function actionIndex() 
  {   
    $article = new Article(); 
    if(Yii::$app->request->get('class')){ 
      $query = Article::find() 
          ->joinWith('articleClass') 
          ->select(['{{%article}}.*,{{%article_class}}.class_name']) 
          ->where(['article_class' => Yii::$app->request->get('class')]); 
      $dataProvider = new ActiveDataProvider([ 
        'query' => $query, 
      ]); 
       
    }else{ 
      $query = Article::find() 
          ->joinWith('articleClass') 
          ->select(['{{%article}}.*,{{%article_class}}.class_name']); 
      $dataProvider = new ActiveDataProvider([ 
        'query' => $query, 
      ]); 
       
    } 
    return $this->render('index', [ 
      'dataProvider' => $dataProvider, 
      'model' => $article, 
    ]); 
  } 

<?= GridView::widget([ 
  'dataProvider' => $dataProvider, 
  'columns' => [ 
    ['class' => 'yii\grid\SerialColumn'], 
    'id', 
    //'article_content:ntext', 
    [ 
      'value'=>'class_name', 
      'label'=>'文章分类', 
    ], 
    'article_title', 
    'article_addtime:datetime', 
    // 'article_updatetime:datetime', 
    // 'article_author', 
    ['class' => 'yii\grid\ActionColumn'], 
  ], 
]); ?>