/** * */ public function setFirst(Content2Type $first = null) { // the size may vary between 1 and 12 and corresponds to // bootstrap container col classes $this->setSize('content-12'); $this->setCollapse(false); if ($first) { $first->setBack($this); $this->next = $first; $this->back = null; } else { $this->next = null; $this->back = null; } }