Yii2 : File Input throws error after submitting form - php

Question

When I click on the Signup button I receive the following error: Array to string conversion.
I think that the error occurs when I call fileInput() method but i don't know how to solve it.
This is the partial code of the view
<?php $form = ActiveForm::begin(); ?>
<?= $form->field($model, 'username')->textInput(['autofocus' => true]) ?>
<?= $form->field($model, 'password')->passwordInput() ?>
<?= $form->field($model, 'email') ?>
<?= $form->field($modelUpload, 'imageFile')->fileInput() ?>
<div class="form-group">
<?= Html::submitButton('Signup', ['class' => 'btn', 'name' => 'signup-button']) ?>
</div>
<?php ActiveForm::end(); ?>
While this is the code for the controller:
<?php
class SiteController extends Controller {
/**
* Signs user up.
*
* #return mixed
*/
public function actionSignup() {
$model = new SignupForm();
$modelUpload = new UploadForm();
if ($model->load(Yii::$app->request->post()) && $modelUpload->load(Yii::$app->request->post())) {
$modelUpload->imageFile = UploadedFile::getInstances($modelUpload, 'imageFile');
if ($user = $model->signup()) {
if (Yii::$app->getUser()->login($user) && $modelUpload->upload()) {
return $this->goHome();
}
}
}
return $this->render('signup', [
'model' => $model,
'modelUpload' => $modelUpload,
]);
}
}
This is the code of the model. It's the same of the official documentation.
<?php
class UploadForm extends Model {
/**
* #var UploadedFile
*/
public $imageFile;
public function rules() {
return [
[['imageFile'], 'file', 'skipOnEmpty' => false, 'extensions' => 'png, jpg'],
];
}
public function upload() {
if ($this->validate()) {
$this->imageFile->saveAs('uploads/' . $this->imageFile->baseName . '.' . $this->imageFile->extension);
return true;
} else {
return false;
}
}
}
?>
Errors:

Answer 1

Instant Solution
Change your line inside the actionSignup() from below
UploadedFile::getInstances($modelUpload, 'imageFile');
to
UploadedFile::getInstance($modelUpload, 'imageFile');
Reason
It's only a single file you are uploading not multiple files so getInstances() should be getInstance()
About
getInstance : Returns an uploaded file for the given model
attribute. The file should be uploaded using
[[\yii\widgets\ActiveField::fileInput()]]
getInstances: Returns all uploaded files for the given model
attribute.

Answer 2

if you want to upload multiple files - having'maxFiles' > 1 in your model's FileValidator rules - change your attribute name from:
<?= $form->field($modelUpload, 'imageFile')->fileInput() ?>
to
<?= $form->field($modelUpload, 'imageFile[]')->fileInput() ?>
read this:
https://www.yiiframework.com/doc/guide/2.0/en/input-file-upload#uploading-multiple-files