code: public static function form($data = [])
      {
          $data = array_merge(self::$default_form, $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 .= '<textarea name="' . $data['name'] . '" placeholder="' . $data['holder'] . '" class="' . $data['class'] . '" style="' . $data['style'] . '" rows="' . $data['rows'] . '" ' . $data['attr'] . '>' . $data['value'] . '</textarea>';
          
          // 提示
          if (! empty($data['tip'])) {
              $html .= '(' . $data['tip'] . ')';
          }
          
          $html .= '</div>';
          $html .= '</div>';
          
          return $html;
      }
docs: form
  
  @param array $data
  @return string