Node::getPreviousSibling

public function getPreviousSibling()
{
	$searchableSibling = null;
	if($this->parentNode)
	{
		$previousSibling = null;
		foreach($this->parentNode->getChildNodesArray() as $sibling)
		{
			if($this->isEqual($sibling))
			{
				$searchableSibling = $previousSibling;
				break;
			}

			$previousSibling = $sibling;
		}
	}

	return $searchableSibling;
}