LOOP: Put a class around every 10 posts.

<!-- the loop-->
<?php if (have_posts()) : ?>

<!-- new variable for post count -->
<?php $c = 0; ?>

<!-- begin THE LOOP -->
<?php while (have_posts()) : the_post(); ?>

<!--open div class-->
<?php if ($c == 0 || $c == 10 || $c == 20 || $c == 30 ) { ?> <div class="slider"> <?php  } ?> 

<!-- increments post count with each post -->
<?php $c++; ?>

<!-- post content -->
<div class="post"><?php the_content(); ?></div>

<!--close div class-->
<?php if ($c == 10 || $c == 20 || $c == 30 ) { ?> </div> <?php  } ?>  

<!-- end of the loop-->
<?php endwhile; else:?>

Obvious problem doesn’t go to infinity,

And a bigger problem is that the div will not close if not a 10th post, so if the post is like 24 will not be able to close the div. But I am sure ill find a work around and update.

<!-- the loop-->
<?php if (have_posts()) : ?>

<!-- new variable for post count -->
<?php $c = 0; ?>

<!-- begin THE LOOP -->
<?php while (have_posts()) : the_post();?>

<!--open div class-->
<?php if( $c == 0) { ?><div class="slider"><?php } ?>

<!-- increments post count with each post -->
<?php $c++; ?>

<!-- post content -->
<div class="post"><?php the_content(); ?></div>

<!--close div class-->
<?php if( $c == 10) {?></div><?php $c = 0;} ?>

<!-- end of the loop-->
<?php endwhile; else:?><?php endif; ?>

<!-- if not ended on a 10th post close div -->
<?php if( $c == 10 || $c == 0) {} else {?></div><?php } ?>

Please let me know if this worked for anyone or if you are having trouble.

Actually, that code I posted was wrong. Don’t use it.