guild/backend/modules/settings/views/skill/_form.php

<?php

use yii\helpers\Html;
use yii\widgets\ActiveForm;

/* @var $this yii\web\View */
/* @var $model backend\modules\settings\models\Skill */
/* @var $form yii\widgets\ActiveForm */
?>

<div class="skill-form">

    <?php $form = ActiveForm::begin(); ?>

    <?= $form->field($model, 'name')->textInput(['maxlength' => true]) ?>
    <?= $form->field($model, 'category_id')->dropDownList(
        \yii\helpers\ArrayHelper::map(\common\models\SkillCategory::getAll(), 'id', 'name')
    ); ?>

    <div class="form-group">
        <?= Html::submitButton('Сохранить', ['class' => 'btn btn-success']) ?>
    </div>

    <?php ActiveForm::end(); ?>

</div>