public function then(\Closure $callback)
    {
        if ($this->ready) {
            return null;
        }

        $this->ready = true;

        if (!$this->checkDomain() || !$this->checkPath() || !$this->checkSecurity()) {
            return null;
        }

        $oNS = parent::$prefixNS;
        $oPP = parent::$prefixPath;

        if ($this->ns) {
            parent::$prefixNS = $this->ns;
        }

        if ($this->path) {
            parent::$prefixPath = rtrim($this->currentPrefixPath, '/');
        }

        call_user_func_array($callback, $this->arguments);

        parent::$prefixNS = $oNS;
        parent::$prefixPath = $oPP;
    }