Symfony getRootDir() + /../folder/file.ext (file_get_contents) not found - symfony

Question

I am virtually at a brick wall with Symfony, I have a folder at /../compiled/ with some minified files, and the controller is configured to get files from getRootDir() + /../compiled/file.min.css
However, it just throws out an exception 'file not found' when call file_get_contents(file) even when the file actually exists.
I just don't know what is wrong, it is such a cryptic problem.
Code as requested:
public function atpInitAction(Request $request) // Validates the origin.
{
$content = null; $_file = $request->query->get('file');
if ($_SERVER["SERVER_NAME"] == atpHandler::getDomain())
{
// I AM FROM THE ORIGIN...
$webfolder = $this->get('kernel')->getRootDir() . '/../compiled';
$_file = $webfolder."/".$_file;
}
// What's my mime?
$_mime = 'text/plain';
if ($_file[strlen($_file)-2] == 'j') { $_mime = 'text/javascript'; }
else { $_mime = 'text/css'; }
$response = new Response();
$response->headers->set('Content-Type', $_mime);
$response->headers->set('Content-Disposition', 'filename="'.basename($_file) . '";');
$response->headers->set('Content-Length', filesize($_file));
$response->setContent(file_get_contents($_file));
$response->sendHeaders();
return $response;
}