Сергей

$db = ModelActiveRecord::findOne();
$db->entry = 123;
$db->save();

$db = new ModelActiveRecord()
$db->entry = 123;
$db->save();

public function rules() {
	return [
		['file', 'file', 'extensions' => ['png', 'jpg', 'gif'], 'maxSize' => 1024 * 1024 * 2],
	];
}

if ($model->load(Yii::$app->request->post()) && !$model->validate()) {
	foreach ($model->getErrors() as $key => $value) {
		echo $key.': '.$value[0];
	}
 return;
}

$.ajax({
      url: url,
      type: 'POST',
      data: new FormData( this ),
      processData: false,
      contentType: false,
      success:function(src) {
         //делаем что-то
      }
    });

$this->redirect('index.php?r=user/profile&id='.$id,302);

'bootstrap' => ['debug'],
'modules' => [
    'debug' => [
        'class' => 'yii\debug\Module',
        'allowedIPs' => ['Айпи']
    ]
];