FluidTYPO3\Flux\Form::add PHP Method

    public function add(Form\FormInterface $child)
    {
        if (FALSE === $child instanceof Form\Container\Sheet) {
            /** @var Form\Container\Sheet $last */
            $last = $this->last();
            $last->add($child);
        } else {
            $children = $this->children;
            foreach ($children as $existingChild) {
                if ($child->getName() === $existingChild->getName()) {
                    return $this;
                }
            }
            $this->children->attach($child);
            $child->setParent($this);
        }
        return $this;
    }