kartik\builder\Form::renderFieldSet PHP Method

    protected function renderFieldSet()
    {
        $content = '';
        $cols = is_int($this->columns) && $this->columns >= 1 ? $this->columns : 1;
        $index = 0;
        $attrCount = count($this->attributes);
        $rows = (double) ($attrCount / $cols);
        $rows = ceil($rows);
        $names = array_keys($this->attributes);
        $values = array_values($this->attributes);
        $width = (int) (self::GRID_WIDTH / $cols);
        Html::addCssClass($this->rowOptions, 'row');
        $skip = $attrCount == 1;
        for ($row = 1; $row <= $rows; $row++) {
            $content .= $this->beginTag('div', $this->rowOptions, $skip);
            for ($col = 1; $col <= $cols; $col++) {
                if ($index > $attrCount - 1) {
                    break;
                }
                $attribute = $names[$index];
                $settings = $values[$index];
                $settings = array_replace_recursive($this->attributeDefaults, $settings);
                $colOptions = ArrayHelper::getValue($settings, 'columnOptions', $this->columnOptions);
                $colWidth = $width;
                if (isset($colOptions['colspan'])) {
                    $colWidth = $colWidth * (int) $colOptions['colspan'];
                    unset($colOptions['colspan']);
                }
                $colWidth = (int) $colWidth;
                Html::addCssClass($colOptions, 'col-' . $this->columnSize . '-' . $colWidth);
                $content .= "\t" . $this->beginTag('div', $colOptions, $skip) . "\n";
                if (!empty($settings['attributes'])) {
                    $this->raise(self::EVENT_BEFORE_RENDER_SUB_ATTR, $attribute, $index, ['settings' => &$settings]);
                    $content .= $this->renderSubAttributes($settings, $index);
                    $this->raise(self::EVENT_AFTER_RENDER_SUB_ATTR, $attribute, $index, ['content' => &$content]);
                } else {
                    $this->raise(self::EVENT_BEFORE_PARSE_INPUT, $attribute, $index, ['settings' => &$settings]);
                    $content .= "\t\t" . $this->parseInput($attribute, $settings, $index) . "\n";
                    $this->raise(self::EVENT_AFTER_PARSE_INPUT, $attribute, $index, ['content' => &$content]);
                }
                $content .= "\t" . $this->endTag('div', $skip) . "\n";
                $index++;
            }
            $content .= $this->endTag('div', $skip) . "\n";
        }
        return $content;
    }