Symfony\Component\Form\FieldGroup::__clone PHP Method

    public function __clone()
    {
        foreach ($this->fields as $name => $field) {
            $field = clone $field;
            // this condition is only to "bypass" a PHPUnit bug with mocks
            if (null !== $field->getParent()) {
                $field->setParent($this);
            }
            $this->fields[$name] = $field;
        }
    }