gan_node_html.php
function getRoot() {
		$r = $this->parent;
		$n = ($r === null) ? null : $r->parent;
		while ($n !== null) {
			$r = $n;
			$n = $r->parent;
		}

		return $r;
	}
function getRoot() {
		$r = $this->parent;
		$n = ($r === null) ? null : $r->parent;
		while ($n !== null) {
			$r = $n;
			$n = $r->parent;
		}

		return $r;
	}
Get top parent
@return DomNode Root, null if node has no parent