Symfony 1.2 to 2.3 migration - symfony

Question

I've got a pretty big Symfony 1.2 project to migrate.
First, I modified my .htaccess so I can have some pages handled by Symfony 2.
What I'd like to do, to make the migration smoother, is to be able to render some SF2 action/templates/methods/... inside SF1.
I added the autoloader to the SF1 app, so I can access to twig rendering methods and other stuff.
But how can I call a SF2 action ?
For example, if I want to migrate only the footer first, I would also need some php methods, not only rendering. That was previously in SF1 component, where should it be now ?
If you've got any suggestion about the way of migrating, don't hesitate !
EDIT 1 :
Apparently, the only way to do something like that is to render a full twig template, and/or in this template call some other partial twig templates with render(url, params).
Here is my SF1 code to be able to render twig templates :
public static function getTwig()
{
require_once __DIR__.'SF2_PATH/vendor/twig/extensions/lib/Twig/Extensions/Autoloader.php';
Twig_Autoloader::register();
$loader = new Twig_Loader_Filesystem( __DIR__.'SF2_PATH/sf2/src/VENDOR/BUNDLE/');
$twig = new Twig_Environment($loader, array(
'cache' => __DIR__.'SF2_PATH/sf2/app/cache/dev/twig',
));
return $twig;
}
And so :
$twig->loadTemplate('header.html.twig');
EDIT 2 :
That doesn't seem to work, if in a twig template I try to render an other one with {{render(controller('BUNDLE:CONTROLER:ACTION', {})) }} for example Twig_Error : The function "controller" does not exist. And if I try to render the url Unknown tag name "render".
I guess Symfony 2 twig functionalities are not loaded, how can I do that ?
EDIT 3 :
Ok, now I can do it, but I've got the following message...
Twig_Error_Runtime An exception has been thrown during the rendering
of a template ("Rendering a fragment can only be done when handling a
master Request.") in ...

Answer 1

EDIT : I solved it !
Here is my full bootstrap method to render a Twig template and be able to use some Symfony 2 functionalities, in Symfony 1.
$loader = require_once __DIR__.'/../../../sf2/app/bootstrap.php.cache';
Debug::enable();
require_once __DIR__.'/../../../sf2/app/AppKernel.php';
$kernel = new AppKernel('dev', true);
$kernel->loadClassCache();
Request::enableHttpMethodParameterOverride();
$request = Request::createFromGlobals();
$kernel->boot();
$kernel->getContainer()->enterScope('request');
$kernel->getContainer()->set('request', new \Symfony\Component\HttpFoundation\Request(), 'request');
$this->container = $kernel->getContainer()->get('twig');