gistfile1.php

    function getCMSFields() {
        $f = new FieldList(
          TextField::create('Title'),
          HTMLEditorField::create('Content'),
          $singleorshow = OptionsetField::create('SingleOrShow','Single Image or Slideshow?', singleton('PageSection')->dbObject('SingleOrShow')->enumValues()),
          $single = DisplayLogicWrapper::create(
            $image = UploadField::create('Image'),
            $imageonleft = CheckboxField::create('ImageOnLeft', 'Tick for a vertical image format'),
            $borderbottom = CheckboxField::create('BorderBottom', 'Tick for no padding below image')
          ),
          $show = DisplayLogicWrapper::create(
            $grid = GridField::create('Slides', 'Slideshow', $this->Slides(), GridFieldConfig_RelationEditor::create())
          )
        );

        
        $single->displayIf("SingleOrShow")->isEqualTo("Single");
        $show->displayIf("SingleOrShow")->isEqualTo("Slideshow");
        return $f;
    }