code: public static function isCollected($model, $modelId, $user_id = null)
      {
          return static::find()->where([
              'user_id' => $user_id ? $user_id : Yii::$app->user->getId(),
              'model_class' => $model,
              'model_id' => $modelId
          ])->exists();
      }
docs: 是否收藏
  @param string $model
  @param integer $modelId
  @param integer $user_id
  @return bool