_isEmpty = $flag; return $this; } public function getIsEmpty() { return $this->_isEmpty; } public function hasIsEmpty() {} public function getChildren() { return $this->_children; } public function setChildren($children) { $this->_children = $children; return $this; } public function hasChildren() { return (count($this->_children) > 0) ? true : false; } public function addChild($child) { $this->_children[] = $child; return $this; } }