single.php  post_class で分岐

<?php get_header(); ?>

<div class="container">
<div class="content">
<?php if(have_posts()): while(have_posts()): the_post(); ?>
<article<?php post_class('kiji'); ?>>
<h1><?php the_title(); ?></h1>
<?php the_content(); ?>
</article>
<?php endwhile; endif; ?>
</div>

</div>
<?php get_footer(); ?>