Check if a post is in specific category to show an icon

Question

I have multiple categories let's call them Group1 (imp1, imp2, imp3) and group2 (cat1, cat2, cat3, cat4).

My posts are in one from the first group of categories and in multiple categories from the second group.

I want to show a small icon in the corner of the post thumbnail if the post is from imp1, or show another icon if the post is from imp2 and so on.

Answer 1

Add post_class() to the post container div:

<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
    <!-- post markup here -->
</div>

...which will give you, among other classes:

• .category-{ID}
• .category-{slug}

You can then target those classes via CSS to add category-specific icons.