public function resolve_paths($file, $use_env = true)
    {
        $files    = array();
        $abs_path = rcube_utils::is_absolute_path($file);

        foreach ($this->paths as $basepath) {
            $realpath = $abs_path ? $file : realpath($basepath . '/' . $file);

            // check if <file>-env.ini exists
            if ($realpath && $use_env && !empty($this->env)) {
                $envfile = preg_replace('/\.(inc.php)$/', '-' . $this->env . '.\\1', $realpath);
                if (is_file($envfile)) {
                    $realpath = $envfile;
                }
            }

            if ($realpath) {
                $files[] = $realpath;

                // no need to continue the loop if an absolute file path is given
                if ($abs_path) {
                    break;
                }
            }
        }

        return $files;
    }