How to get node id on hook_page_build(&$page)

Question

I wrote a hook like so:

function john_page_build(&$page)
{
  $akeys = array_keys($page['content']['system_main']['nodes']);
  print $akeys[0];
}

On pages with urls like http://mysite.com/page/43, it will print the node id for that page. However, on a page with url like http://mysite.co/page/43/done?sid=2, drupal gives a warning saying that $page['content']['system_main']['nodes'] does not exist.

Is there a consistent way to get the node id WITHOUT parsing the url?

Answer 1

Still comes through the URL indirectly, but this is the easiest way to get it: menu_get_object.

<?
if ($node = menu_get_object()) {
 $nid = $node->nid;
}
?>

Note that if there is a node, it was already loaded by the menu system anyway and this is loaded from the static cache.

Refer this discussion for more detail.

Answer 2

Never use arg() in d7 (by chx)! To get actual node, use menu_get_object(), on node pages this will return the complete $node object.

Answer 3

To get nid in your hook from url, you can use arg() function as below

function john_page_build(&$page)
{
  $nid = arg(1);
  echo $nid;
}