<?= $form->field($model, 'Language')->dropDownList(ArrayHelper::map(Doodles::getLanguages(), "Language", "language"), ['class'=>'form-control','prompt' => 'Выберите язык'])->label('Язык') ?>

return Doodles::findBySql('select distinct language from doodles')->asArray()->all();

<select id="utdoodles-language" class="form-control" name="Doodles[Language]">
<option value="">Choose language</option>
<option value="" selected="">en</option>
</select>

return Doodles::findBySql('select distinct language from doodles')->asArray()->all();

Doodles::find()->select('language')->distinct()->asArray()->all();