Why can't $app->run(); work in Yii?

Question

Yii

Good evening!
I have such a problem, I uploaded a Yii site to the hosting, and for the first time I encountered a white screen, I give the index.php input code :

define('YII_DEBUG', true);
if($_SERVER['HTTP_HOST'] == 'visakaz'){
    $yii = dirname(__FILE__).'/framework/yii.php';
    $config = dirname(__FILE__).'/protected/config/dev.php';
    // remove the following lines when in production mode
    defined('YII_DEBUG') or define('YII_DEBUG',true);
}
// Иначе выключаем режим отладки и подключаем рабочую конфигурацию
else {
    echo 1;
    $yii = dirname(__FILE__).'/framework/yiilite.php';
    echo 2;
    $config = dirname(__FILE__).'/protected/config/production.php';
    echo 3;
}
// specify how many levels of call stack should be shown in each log message
defined('YII_TRACE_LEVEL') or define('YII_TRACE_LEVEL',3);
echo 4;
require_once($yii);
echo 5;
$app = Yii::createWebApplication($config);
echo 6;
$app->run();
echo 7;

Now 123456 appeared on a white screen
7 is missing, apparently the problem is in
$app->run();