/**
* Set the parent Fieldset instance
*
* @param Fieldset parent fieldset to which this belongs
* @return Fieldset
*/
public function set_parent(Fieldset $fieldset)
{
if (!empty($this->fieldset_parent)) {
throw new \RuntimeException('Fieldset already has a parent, belongs to "' . $this->parent()->name . '".');
}
$children = $fieldset->children();
while ($child = array_shift($children)) {
if ($child === $this) {
throw new \RuntimeException('Circular reference detected, adding a Fieldset that\'s already a child as a parent.');
}
$children = array_merge($child->children(), $children);
}
$this->fieldset_parent = $fieldset;
$fieldset->add_child($this);
return $this;
}
