private function fetchForm() : bool
    {
        // Get the field keys
        $form_key = preg_grep('/^form_' . preg_quote($this->name, '/') . '_[a-f0-9]+$/', array_keys($_SESSION));
        if (empty($form_key)) {
            return false;
        }
        $this->key = array_values($form_key)[0];

        // Save properties
        foreach ($_SESSION[$this->key] as $key => $value) {
            if (substr($key, -2) === '[]') {
                $this->keys[substr($key, 0, -2)] = $value;
            } else {
                $this->keys[$key] = $value;
            }
        }
        return true;
    }