use of yii controller in legacy apps

controller.php

<?php

function getController()
{
    static $controller = null;
    
    if ($controller == null) {
        $tmp = Yii::app()->createController('site/index');
        $controller = $tmp[0];
        $controller->init();
    }
    
    return $controller;
}

getController()->renderPartial('index');