Conditional tag

Question

I am using this code to show custom code on single posts.

function post_footer() {
if (is_single())
{
?>
<div class="custom">
    <h1><a href="<?php the_field('live_demo'); ?>" target="_blank">Live Demo of <?php the_title(); ?><h1>
            <h1><a href="<?php the_field('download'); ?>" target="_blank">Download<h1>
</div>
<?php
}}

How to edit so div should appear only on single post of specified categories, not on all posts.

Answer 1

If it is a single page: is_single() returns TRUE.

If a $post is in a specific category: in_category( $cat ) returns TRUE. It needs $cat as ID, name or (string) slug.

Anyway: Searching for a list of conditional tags isn´t that hard.