“新建表单模型”的思路没问题。假设:

• 表单模型为 PostForm, 内容大致如下:

  class PostForm extends \yii\base\Model
  {
      // 存储 Post 模型中的字段
      public $title; 
      // 存储 PostExtra 模型中的字段
      public $content;
      // 存储 PostAttachment 模型中的字段
      public $imgUrl;
    
      public function rules()
      {
          // ...
      }
  }
  

• 一个 Post 对应一个 PostExtra;

• 一个 Post 对应一个 PostAttachment;

帖子修改操作的控制器代码大致如下：

class PostController extends \yii\web\Controller
{
    public function actionUpdate($id)
    {
        $post = Post::findOne($id);
        $extra = $post->extra;
        $attachment = $post->attachment;

        $postForm = new PostForm();
        $postForm->title = $post->title;
        $postForm->content = $extra->content;
        $postForm->imgUrl = $attachment->imgUrl;

        if ($postForm->load(Yii::$app->request->post()) && $postForm->validate()) {
            // 写入修改后的数据
        }

        return $this->render('update', ['postForm' => $postForm]);
    }
}

“多模型同时输入”也可以。你觉得“别扭”的三个 &&:

• load() && load()
• validate() && validate()
• save() && save()

前两个是必须的，最后一个可以放在一个事务内。过程大致如下：

class PostController extends \yii\web\Controller
{
    public function actionUpdate($id)
    {
        $post = Post::findOne($id);
        $extra = $post->extra;
        $attachment = $post->attachment;

        if (
            $post->load(Yii::$app->request->post()) 
            && $post->validate()
            && $extra->load(Yii::$app->request->post()) 
            && $extra->validate()
            && $attachment->load(Yii::$app->request->post()) 
            && $attachment->validate()
        ) {
            $transaction = Yii::$app->db->beginTransaction();
            try {
                if (!$post->save(false)) {
                    throw new \yii\db\Exception('Failed to insert xxx.');
                }
                if (!$extra->save(false)) {
                    throw new \yii\db\Exception('Failed to insert xxx.');
                }
                if (!$attachment->save(false)) {
                    throw new \yii\db\Exception('Failed to insert xxx.');
                }
        
                $transaction->commit();

                return $this->redirect('index');

            } catch(\Exception $e) {
                $transaction->rollBack();
                throw $e;
            }
        }

        return $this->render('update', [
            'post' => $post,
            'extra' => $extra,
            'attachment' => $attachment,
        ]);
    }
}