How to correctly update records from a table?

Question

Yii

Trying to edit a post
$postData = $this->request->post();
$model->load($postData);
$model->validate();
$model->save();
Why with $model->save(); there is an attempt to insert a new record, and not update an existing one, because it is already loaded from the POST? id(primary key) is there.

Answer 1

When you load data into a model from a post, they are simply loaded into attributes and that's it, no search among already created models by default occurs. Accordingly, if you want to edit the model, you must:
1. First find it
2. Then load the data from the post
3. Save

Answer 2

Apparently you are creating a new object instance.

public function actionUpdate($id)
{
  $model = Model::findOne($id);
  if ($model === null) {
    //exception
  }
  $model->load(Yii::$app->request->post());
  $model->save();
  return $this->render ....
}

Answer 3

if so:

$model = new SomeModel();
$model->save();

we have a new record, since a new model instance has been created, empty, without an id and $model->isNewRecord returns true
and if so:

$model = SomeModel::find()->one();
$model->save();

then this model has an id and the $model->isNewRecord method returns false and therefore the data with a certain id will be updated