Setting A Header Image for a Wordpress Page and all its children

Question

Wordpress. I've got a handful of pages, each with children -- varying depths.

Let's say it's like this:

+about
-- page1
-- page2
+stuff
-- page1
--- sub-sub-page
-- page2

My problem: I want to set a graphic header for all the "about" pages, including all its children... and a different graphic header for all "stuff" pages and all its children.

I could do this using a custom field for each individual page, but I don't trust my users to remember to set this field.

I thought about adding to the page.php template and telling the page to find its parent top-level page to determine which "family" it's in, then set the header graphic that way...but I don't want to invest a ton of time (and run-time) resources traversing up the hierarchy.

Any ideas?

Much thanks in advance...

UPDATE:

Taking the code from below, I modified it to use outside of the Wordpress Loop (have not yet integrated the "default" value yet).

    <?php 
    global $wp_query;
$postid = $wp_query->post->ID;

$header_swf = get_post_meta($postid, 'header_swf', true);

if (!$header_swf) {
    $parent = get_page($wp_query->post->post_parent); //array of values for this page's parent, directly above it

   while (!$header_swf && $parent) {
        $header_swf = get_post_meta($parent->ID, 'header_swf', true);
        $parent = get_page($parent->post_parent); //new parent
    }

}

?>

Answer 1

I'd say test for the current page's family. I wouldn't think it'd be too taxing, as it's just a simple short-circuit.

Here's a previous SO thread on how you'd accomplish this.

Answer 2

Note: This answer assumes (perhaps incorrectly) there is no built-in method to do this.

You could write something in the template that looked for a predefined custom field. If none exists, it could ask the parent page for its version of the custom field, and so on.

$val = get_post_custom_values('header_image');
if (!val) {
    $parent = get_page($post->post_parent);
    while (!$val && $parent) {
        $val = get_post_custom_values('header_image', $parent->id);
        $parent = get_page($parent->post_parent);
    }
    if (!$parent && !val) // has failed to find a header image!
        $val = 'my default value';
}

Or something like that.....

I should point out that might be really database heavy so it might be worth caching the value for each given URL. I'd personally recommend memcached but there are other methods.