function make_filename($filename)
    {
        // Check if it's an absolute or relative path.
        if (pia_substr($filename, 0, 1) != '/') {
            $filename = $this->root . '/' . $filename;
        }

        if (!file_exists($filename)) {
            die("Template->make_filename(): Erreur - Le fichier $filename est inexistant");
        }
        return $filename;
    }