Adding a different class to every third post?

The following code should add the class “third” to every 3rd post:

<?php if (have_posts()) : ?>
<>?php $c = 0;while (have_posts()) : the_post(); $c++;
if( $c == 3) {
	$style = 'third";
	$c = 0;
}
else $style='';
?>
<div <?php post_class($style) ?> id="post-<?php the_ID(); ?>">

Not sure what you looked at (I couldn’t find the Post Classes function).

But I did something similar on my theme. Use this in The Loop inside the php file(s) in question (most likely home, index, category, and archive) and it should work.

<?php if (have_posts()) : ?>
	<!-- new variable for post count -->
	<?php $i = 1; ?>

	<!-- begin THE LOOP -->
	<?php while (have_posts()) : the_post(); ?>
   			<!-- increments post count with each post -->
	    	<?php $i++; ?>

	        <div class="<?php the_ID(); ?><?php if ($i == 3 || $i == 6 || $i == 9 || $i == 12 ) { ?> thirdpost_class<?php  } ?>">
	        <h2 class="archive-header"><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title() ?></a></h2>
	                <a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">
						<?php the_title();?>
					</a>
	        		<?php the_excerpt(); ?>
	        		<p class="postmetadata"><?php the_time('M d, Y') ?></p>
	        </div>
<!-- end THE LOOP -->
<?php endwhile; ?>
<?php endif; ?>

Also, see The Loop in Action for more detail on how to customize The Loop.

Thanks so much for taking the time to reply to this thread esmi and mrengy.

I have tried both pieces of code, and i can’t get either of them to work. The new class doesn’t attach to the third post, and when i view the source code it isn’t present any where. Have you got any idea of what could be causing the issue?

Thanks once again

It might help if you dropped a copy of the file into the WordPress pastebin and post the pastebin url here.

esmi some of your code had errors, correction below.

<?php if (have_posts()) : ?>
<?php $c = 0;while (have_posts()) : the_post(); $c++;
if( $c == 3) {
	$style = 'third';
	$c = 0;
}
else $style='';
?>
<div <?php post_class($style) ?> id="post-<?php the_ID(); ?>">

seanjacob, thanks thats just what I was looking for, works a treat!