if is a page, or a child of a page, or in a category (a solution)

I wanted to share this from a website I’m working on right now, just in case anyone else might be looking for such a solution. It may or may not be the best approach, but it works for me, and seems simple enough.

This checks to see if the current screen is a specific page or a child of a specific page or (if a post) is in a specific category — and has different sets of criteria.

So, if one set criteria is matched, it’ll do one thing; if another set is matched, it’ll do another. I used this for different sets of navigation in the header template:

<?php if (is_page('page_name_1') || $post->post_parent=="77" || in_category(3) ) { $children = '<a href="/page_slug_1/">Page One</a><ul><li><a href="/page_slug_2/">Page Two</a></li><li><a href="/page_slug_3/">Page Three</a></li></ul></li>' . wp_list_pages("title_li&child_of=77&echo=0"); }
elseif (is_page('page_name_2') || $post->post_parent=="75" || in_category(4) ) { $children = '<a href="/page_slug_2/">Page Two</a><ul><li><a href="/page_slug_1/">Page One</a></li><li><a href="/page_slug_3/">Page Three</a></li></ul></li>' . wp_list_pages("title_li&child_of=75&echo=0"); }
elseif (is_page('page_name_3') || $post->post_parent=="73" || in_category(5) ) { $children = '<a href="/page_slug_3/">Commercial</a><ul><li><a href="/page_slug_1/">Page One</a></li><li><a href="/page_slug_2/">Page Two</a></li></ul></li>' . wp_list_pages("title_li&child_of=73&echo=0"); }
if ($children) { ?>
<ul id="suckerfishnav">
	<?php echo $children; ?>
</ul>
<?php } ?>

And I used this in the page and single post templates to show posts from a certain category depending on what criteria was matched:

<?php if (is_page('page_name_1') || $post->post_parent=="77" || in_category('3')) {
		$my_query = new WP_Query('category_name=cat_slug_name3');
		}
	elseif (is_page('page_name_2') || $post->post_parent=="75" || in_category('4')) {
		$my_query = new WP_Query('category_name=cat_slug_name4');
		}
	elseif (is_page('page_name_3') || $post->post_parent=="73" || in_category('5')) {
		$my_query = new WP_Query('category_name=cat_slug_name5');
		}
	while ($my_query->have_posts()) : $my_query->the_post(); ?>

	<div class="post">
		<div class="title"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></div>
		<div class="serif"><em><?php the_meta(); ?></em></div>
	</div>

<?php endwhile; ?>

I hope this helps someone!