Working with Yii files Where is the mistake?

Question

Yii

Good afternoon. You need to access the file in the application. To do this, I need to upload it through the form. Created a form according to one of the guides on the official YiiFramework website.
Model

public $imageFile;

    public function rules()
    {
        return [
            );
$form->field($file, 'imageFile')->fileInput();

ActiveForm::end();

As a result, I get not a file upload form, but

Call to a member function formName() on a non-object

Searched many forums, so far nothing has helped!

Answer 1

$form->field($file, 'imageFile')->fileInput();
$file - exactly the yii\base\Model instance in the view?

Answer 2

<?= $form->field($model, 'imageFiles[]')->fileInput(['multiple' => true, 'accept' => 'image/*']) ?>

You should have $model there, not $file