Extending an existing web application using Codeigniter4

I need to work with the native php session since the existing application might break if I switch to Codeigniter session. 

I tried looking into config files to see if CI session can be disabled. I did not find any config parameter. After trying to work along the error message, I was able to load the welcome page by commenting out the following lines in system/Common.php lines 981 to 989 like so:

function session(?string $val = null)
    {  /*
        $session = Services:ession();

        // Returning a single item?
        if (is_string($val)) {
            return $session->get($val);
        }

        return $session; */
        return true;
    }

It works but I am not sure if its the right thing to do.