yii\widgets\MaskedInput::init PHP Method

    public function init()
    {
        parent::init();
        if (empty($this->mask) && empty($this->clientOptions['alias'])) {
            throw new InvalidConfigException("Either the 'mask' property or the 'clientOptions[\"alias\"]' property must be set.");
        }
    }

 public function init()
 {
     /* @var $formatter Formatter */
     $formatter = Yii::$app->formatter;
     if ($this->mask === null) {
         $this->mask = Yii::$app->formatter->pasportNomerFormat;
     }
     parent::init();
     $formatter->nullDisplay = '';
     $this->model->{$this->attribute} = $formatter->asPasportNomer($this->model->{$this->attribute});
 }