<?php

namespace app\controllers;

use yii\web\Controller;

use yii\db\Connection;

use Yii;

class MyController extends Controller

{

    public function actionIndex()

    {

        $country = Yii::$app -> db -> createCommand("select * from country") -> queryAll();

        print_r($country);

    }

}

<?php

return [

    'class' => 'yii\db\Connection',

    'dsn' => 'mysql:host=localhost;dbname=yii',

    'username' => 'root',

    'password' => '12',

    'charset' => 'utf8',

];