Post navigation with category check

Proper working post navigation with post titles and customisation.

Also includes parent category check.

<?php if ( in_category( ‘articles’ ) && is_single() ) { ?>
<div class=”post-nav clearfix”>
<span class=”left”><?php next_post(‘&laquo; %’, ”, ‘yes’); ?></span>
<span class=”right”><?php previous_post(‘% &raquo;’, ”, ‘yes’); ?></span>
</div>
<?php } ?>