protected function _get_input_html(array $params = array())
 {
     $attrs_html = self::_get_attr_html_exclude($params, array('onclick', 'onchange', 'value'));
     $checkbox_attrs_html = self::_get_attr_html_only($params, array('onclick', 'onchange'));
     $input_html = "<{$this->_tagname}{$attrs_html}>";
     if (!empty($this->_options)) {
         $list_html = array();
         foreach ($this->_options as $option) {
             $option_tag = new HTMLInputCheckboxControl($this->get_name() . '[]', $option['label'], in_array($option['value'], $this->_selected_values), $option['value']);
             $option_tag->update_params($checkbox_attrs_html);
             $option_tag->set_id($this->get_name() . '_' . $option['value']);
             $list_html[] = $option_tag->to_string();
         }
         $need_count = ceil(count($list_html) / $this->_columns) * $this->_columns;
         while (count($list_html) < $need_count) {
             $list_html[] = self::$_DEFAULT_FILL_CELL_HTML;
         }
         $col_md = floor(12 / $this->_columns);
         $table = array();
         $row = array();
         foreach ($list_html as $cell) {
             $row[] = $cell;
             if (count($row) == $this->_columns) {
                 $table[] = $row;
                 $row = array();
             }
         }
         if ($this->_sort_type == self::SORT_ROWS) {
             $count_cols = count($table[0]);
             $count_rows = count($table);
             $list_index = 0;
             for ($index_col = 0; $index_col < $count_cols; $index_col++) {
                 for ($index_row = 0; $index_row < $count_rows; $index_row++) {
                     $table[$index_row][$index_col] = $list_html[$list_index];
                     $list_index++;
                 }
             }
         }
         foreach ($table as $row) {
             $input_html .= "<div class='row'>";
             foreach ($row as $cell) {
                 $input_html .= "<div class='col-md-{$col_md}'>{$cell}</div>";
             }
             $input_html .= "</div>";
         }
     }
     $input_html .= "</{$this->_tagname}>";
     return $input_html;
 }