code: public static function form($data = [])
      {
          $data = array_merge(self::$default_form, $data);
          $data['uuid'] = md5(serialize($data));
          
          $html = '<div class="am-g am-margin-top-sm">';
          $html .= '<div class="am-u-sm-' . $data['l_sm_num'] . ' am-u-md-' . $data['l_md_num'] . ' am-text-right">' . $data['title'] . '</div>';
          $html .= '<div class="am-u-sm-' . $data['r_sm_num'] . ' am-u-md-' . $data['r_md_num'] . ' am-u-end">';
          
          $html .= '<div class="am-input-group nd-input-file-area">';
          $html .= '<input type="text" class="am-input-sm" name="' . $data['name'] . '" value="' . $data['value'] . '" id="upload_file_' . $data['uuid'] . '" />';
          $html .= '<span class="am-input-group-btn">';
          $html .= '<div class="am-form-group am-form-file">';
          $html .= '<button type="button" class="am-btn am-btn-sm am-btn-default">';
          $html .= '<i class="am-icon-cloud-upload"></i>';
          $html .= '<span>选择文件</span>';
          $html .= '</button>';
          $html .= '<input type="file" class="nd-upload-file" nd-target="upload_file_' . $data['uuid'] . '" nd-option=\'' . $data['option'] . '\' />';
          $html .= '</div>';
          $html .= '</span>';
          $html .= '</div>';
          
          $html .= '</div>';
          $html .= '</div>';
          
          return $html;
      }
docs: form
  
  @param array $data
  @return string