Александр Зеленин

public function getCityList($cat_id) { // could be a static func as well
        $models = \common\models\City::find()->where(['country_id' => $cat_id])->asArray()->all();
        return ArrayHelper::map($models, 'id', 'name_ru','country_id');
       }

git clone
composer install
yii init
#правите локальные конфиги (прописываете базу)
yii migrate

git pull
composer install
yii migrate

/**
     * @var array|\Closure the HTML attributes for the data cell tag. This can either be an array of
     * attributes or an anonymous function that ([[Closure]]) that returns such an array.
     * The signature of the function should be the following: `function ($model, $key, $index, $gridView)`.
     * A function may be used to assign different attributes to different rows based on the data in that row.
     *
     * @see \yii\helpers\Html::renderTagAttributes() for details on how attributes are being rendered.
     */
    public $contentOptions = [];