public function add($name, $value = null)
    {
        $name = self::normalizeName($name);
        $value = self::normalizeValue($value);

        if (!isset($this->parameters[$name])) {
            $this->parameters[$name] = [];
        } elseif (!is_array($this->parameters[$name])) {
            $this->parameters[$name] = (array) $this->parameters[$name];
        }

        $this->parameters[$name][] = $value;
    }