src/Combo.php
public function init()
    {
        parent::init();

        // Set language
        if ($this->language === null && ($language = Yii::$app->language) !== 'en-US') {
            $this->language = substr($language, 0, 2);
        }
        if (!$this->_return) {
            $this->return = ['id'];
        }
        if (!$this->rename) {
            $this->rename = ['text' => $this->name];
        }
        if (!$this->inputOptions['id']) {
            $this->inputOptions['id'] = Html::getInputId($this->model, $this->attribute);
        }
        if ($this->multiple) {
            $this->inputOptions['multiple'] = true;
        }
        if ($this->inputOptions['readonly']) {
            // According to the HTML specification, the `select` element does not support
            // property `readonly`. Solution: render `readonly` field as disabled and prepend hidden
            // input to submit the attribute value.
            $this->inputOptions['disabled'] = true;
        }
        if (!$this->inputOptions['data-combo-field']) {
            $this->inputOptions['data-combo-field'] = $this->name;
        }
        if (!isset($this->inputOptions['unselect'])) {
            $this->inputOptions['unselect'] = null;
        }
    }
public function init()
    {
        parent::init();

        // Set language
        if ($this->language === null && ($language = Yii::$app->language) !== 'en-US') {
            $this->language = substr($language, 0, 2);
        }
        if (!$this->_return) {
            $this->return = ['id'];
        }
        if (!$this->rename) {
            $this->rename = ['text' => $this->name];
        }
        if (!$this->inputOptions['id']) {
            $this->inputOptions['id'] = Html::getInputId($this->model, $this->attribute);
        }
        if ($this->multiple) {
            $this->inputOptions['multiple'] = true;
        }
        if ($this->inputOptions['readonly']) {
            // According to the HTML specification, the `select` element does not support
            // property `readonly`. Solution: render `readonly` field as disabled and prepend hidden
            // input to submit the attribute value.
            $this->inputOptions['disabled'] = true;
        }
        if (!$this->inputOptions['data-combo-field']) {
            $this->inputOptions['data-combo-field'] = $this->name;
        }
        if (!isset($this->inputOptions['unselect'])) {
            $this->inputOptions['unselect'] = null;
        }
    }
{@inheritdoc}