How can I load the title of parent item in Drupal - php

Question

I want to extend Nodes with the title of the parentnode so I can display a hierarchy link.
I have a solution that sometimes works:
function modulename_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL)
{
switch ($op)
{
case 'view':
loadParentTitle($node);
break;
}
}
function loadParentTitle(&$node)
{
$title = $node->title;
$query = "SELECT mlid, p1, p2,p4,p5,p6,p7,p8,p9 FROM menu_links WHERE link_title like '%%%s%%'";
$data = db_fetch_array(db_query($query, $title));
$mlid = $data["mlid"];
$i = 9;
while (($data["p". $i] == 0 || $data["p". $i] == $mlid) && $i >= 0)
{
$i--;
}
if ($i > 0)
{
$query = "SELECT `link_title` as parentTitle from `menu_links` WHERE mlid = " . $data["p" . $i];
$data = db_fetch_array(db_query($query));
$parentTitle = ($data["parentTitle"]);
}
else
{
$parentTitle = $title;
}
$node->content['#parentTitle'] = $parentTitle;
}
This works as long as the title of the item is the same as the Menu Title. However i'm looking for a solution that will work all the time. Any ideas?

Answer 1

You did not specify really what do you mean by 'parent node' but the mlid of the parent of a menu link is stored in menu_links.plid. Now, the link_path is going to be node/nid and you can fetch the title from there.
$mlid = db_result(db_query("SELECT plid FROM {menu_links} WHERE link_path = 'node/%d'", $node->nid));
$link_path = db_result(db_query("SELECT link_path FROM {menu_links} WHERE mlid = %d", $mlid));
$title = db_result(db_query("SELECT title FROM {node} WHERE nid = %d", substr($link_path, 5));
The first two queries can be unified by a JOIN but I strongly recommend against getting the third in there too (you can with CONCAT('node/', nid) = parent.link_path) because that is not going to be indexable. These three queries should be practically instant.
P.S. You won't forget to check_plain($title) before printing, would you? :)