yf_form2_validate class

    public function _input_assign_params_from_validate($extra = [], $form = null)
    {
        $name = $extra['name'] ?? '';
        $is_html_array = (false !== strpos($name, '['));
        if ($is_html_array) {
            $name = str_replace(['[', ']'], ['.', ''], trim($name, ']['));
        }
        $vr = &$form->_validate_rules_names[$name];

        // Useful for testing server-side validation
        if (conf('form_no_js_validation')) {
            return $extra;
        }
        if (isset($vr['required']) || isset($vr['captcha'])) {
            $extra['required'] = 1;
            $extra['class_add_form_group'] = trim(($extra['class_add_form_group'] ?? null) . ' ' . $form->CLASS_REQUIRED);
        }
        foreach (['ajax_is_unique', 'ajax_is_unique_without', 'ajax_exists'] as $rule) {
            $_rule = str_replace('ajax_', '', $rule);
            if (isset($vr[$rule])) {
                $extra['data-ajax-validate'][$_rule] = $vr[$rule];
            }
        }
        foreach (['ajax_is_unique', 'ajax_is_unique_without', 'ajax_exists'] as $rule) {
            $_rule = str_replace('ajax_', '', $rule);
            if (isset($vr[$rule])) {
                $extra['data-ajax-validate'][$_rule] = $vr[$rule];
            }
        }

        if (conf('form_advanced_js_validation') && $extra['required']) {
            $extra['data-fv-notempty'] = 1;
            $extra['class_add_form_group'] = trim($extra['class_add_form_group'] . ' has-feedback fv-has-tooltip');
        }

        return $extra;
    }