Menu dropdown to select languages Demo
composer require pceuropa/yii2-language-selection-widget dev-master
use pceuropa\languageSelection\LanguageSelection;
<?= LanguageSelection::widget([
'language' => ['pl', 'en', 'fr', 'nl', 'de'],
'languageParam' => 'language',
'container' => 'li', // li for navbar, div for sidebar or footer example
'classContainer' => 'dropdown-toggle' // btn btn-default dropdown-toggle
]) ?>