src/Forms/ReviewContentHandler.php
public function Form($object)
    {
        $placeholder = _t(__CLASS__ . '.Placeholder', 'Add comments (optional)');
        $title = _t(__CLASS__ . '.MarkAsReviewedAction', 'Mark as reviewed');

        $fields = FieldList::create([
            HiddenField::create('ID', null, $object->ID),
            HiddenField::create('ClassName', null, $object->baseClass()),
            TextareaField::create('Review', '')
                ->setAttribute('placeholder', $placeholder)
                ->setSchemaData(['attributes' => ['placeholder' => $placeholder]])
        ]);

        $action = FormAction::create('savereview', $title)
            ->setTitle($title)
            ->setUseButtonTag(false)
            ->addExtraClass('review-content__action btn btn-primary');
        $actions = FieldList::create([$action]);

        $form = Form::create($this->controller, $this->name, $fields, $actions)
            ->setHTMLID('Form_EditForm_ReviewContent')
            ->addExtraClass('form--no-dividers review-content__form');

        return $form;
    }
public function Form($object)
    {
        $placeholder = _t(__CLASS__ . '.Placeholder', 'Add comments (optional)');
        $title = _t(__CLASS__ . '.MarkAsReviewedAction', 'Mark as reviewed');

        $fields = FieldList::create([
            HiddenField::create('ID', null, $object->ID),
            HiddenField::create('ClassName', null, $object->baseClass()),
            TextareaField::create('Review', '')
                ->setAttribute('placeholder', $placeholder)
                ->setSchemaData(['attributes' => ['placeholder' => $placeholder]])
        ]);

        $action = FormAction::create('savereview', $title)
            ->setTitle($title)
            ->setUseButtonTag(false)
            ->addExtraClass('review-content__action btn btn-primary');
        $actions = FieldList::create([$action]);

        $form = Form::create($this->controller, $this->name, $fields, $actions)
            ->setHTMLID('Form_EditForm_ReviewContent')
            ->addExtraClass('form--no-dividers review-content__form');

        return $form;
    }
Bootstrap the form fields for the content review modal

@param DataObject $object
@return Form