Language switcher example

LanguageSwitcher.php

<?php

namespace frontend\components;

use Yii;
use yii\bootstrap\Dropdown;

class LanguageSwitcher extends Dropdown {
    private static $_labels;

    private $_isError;

    public function init() {
        $route = Yii::$app->controller->route;
        $params = $_GET;
        $this->_isError = $route === Yii::$app->errorHandler->errorAction;

        array_unshift($params, '/' . $route);

        foreach (Yii::$app->urlManager->languages as $language) {
            $isWildcard = substr($language, -2) === '-*';
            if ($isWildcard) {
                $language = substr($language, 0, 2);
            }
            $params['language'] = $language;
            $params['url-language'] = $language;
            $this->items[] = [
                'label' => self::label($language),
                'url'   => $params,
            ];
        }
        parent::init();
    }

    public function run() {
        // Only show this widget if we're not on the error page
        if ($this->_isError) {
            return '';
        } else {
            return parent::run();
        }
    }

    public static function label($code) {
        if (self::$_labels === null) {
            self::$_labels = [
                'nl' => 'Nederlands',
                'en' => 'English',
            ];
        }

        return isset(self::$_labels[$code]) ? self::$_labels[$code] : null;
    }
}