Make posts use Category header.

Hi guys, I have a request for something I believe it’s not doable in WordPress.

I simply want to have all the posts under a particular category to use the same layout or header at least. I have custom design for all my categories. Using category-id.php … I have 50 categories and it took me quite some time .. but it’s relatively easy to maintain, surprisingly. I recently came up with a way to custom search in categories, however, as soon as you select the post, it comes back to the typical layout and it’s using get_header() …, Which is a very broad search, considering that I have 514 categories and over 10k posts.

So my question basically is..

I want all the posts under category .. bananas .. which is a subcategory of the category fruit to display my custom header … bananas_header.php

So basically .. you’re located at : http://www.testdomain.com/fruit/bananas/test-post … and that particular post is using the bananas_header.php

Is there a way? I spent 2 hours in the codex without any success.