CMS PHP eval page: change title via code

[anzs]

Hello,

Is it possible to change the page title for CMS PHP evaluation page in the evaluation code somehow? For example:

if (...)
{
  $output = "...";
  [?page title?] = '...'
}
else
{
  $output = "...";
  [?page title?] = '...'
}

What should I use instead of [?page title?] in order to set both title and html_title dynamically?

I was not able to find a solution for this simple issue during more than 5 hours. OOP implementation in PHP is complete mess and working with it is a pure hell. Please help me!

Why do I need that: I would like the CMS article page title and content change depending on GET request parameters.

I started by setting $this->html_title and $this->title in the evaluation code; for sure this did not provide any results.
As a workaround, I tried to override getTitle and getHtmlTitle methods in vBCms_Item_Content_PhpEval class. I found that vBCms_Controller_Content class gets CMS article title (page title) from gvBCms_Item_Content_PhpEval instance, and gets HTML title from its parent class (different instance!) - vBCms_Item_Content class. Such way, vBCms_Controller_Content creates two instances of the same CMS article class - parent and derived class instances, populates them both and takes some properties from one, and other properties from another. I don't have an idea about such OOP patterns.
Please help.