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Perishable Press

Horizontally Sequenced Display Order for WordPress Posts in Two Columns

Most WordPress-powered blogs display posts in sequential order within a single column. Like this, for example:

[ Diagram: Default WordPress Post Display Order ]

But what if you wanted to display your posts in two columns, sequentially ordered from left to right? For example:

[ Diagram: Horizontally Sequenced WordPress Post Display Order ]

This is easily accomplished using two default loops and the rewind_posts() function. The first loop will display the posts in the first column, while the second loop will display the posts in the second column. To do this, we use PHP’s modulus operator to filter out every other post from the first loop, which will display posts as follows:

  • the first most recent post
  • the third most recent post
  • the fifth most recent post

..and so on. Meanwhile, the second loop will feature all of the posts that were filtered out of the first loop:

  • the second most recent post
  • the fourth most recent post
  • the sixth most recent post

and so on, depending on the specified number of displayed posts. As you can see, this configuration divides the posts into “odd” and “even” groups. Note that there is nothing inherently “odd” or “even” about the posts in either group; we are arbitrarily assigning “oddness” and “evenness” based on location of each post within the default sequence. Thus, posts with odd-numbered IDs may appear in the “even” loop and vice versa. having said that, let’s examine the code that will make this happen:

<?php if (have_posts()) : while(have_posts()) : $i++; if(($i % 2) == 0) : $wp_query->next_post(); else : the_post(); ?>

<div id="left-column">
<h1><?php the_permalink(); ?></h1>
<?php the_content(); ?>
</div>

<?php endif; endwhile; else: ?>
<div>Alternate content</div>
<?php endif; ?>

<?php $i = 0; rewind_posts(); ?>

<?php if (have_posts()) : while(have_posts()) : $i++; if(($i % 2) !== 0) : $wp_query->next_post(); else : the_post(); ?>

<div id="right-column">
<h1><?php the_permalink(); ?></h1>
<?php the_content(); ?>
</div>

<?php endif; endwhile; else: ?>
<div>Alternate content</div>
<?php endif; ?>

With that code in place, oddly numbered posts will appear within a division identified with an attribute of id="left-column". Likewise, even-numbered posts will appear within a division identified with an attribute of id="right-column". Thus, we may apply the following CSS to position the divisions as two adjacent columns:

div#left-column {
	width: 333px;
	float: left;
	clear: none;
	}
div#right-column {
	width: 333px;
	float: right;
	clear: none;
	}

Of course, when it comes to configuring the WordPress loop and styling your page with CSS, anything is possible. Feel free to experiment and adapt this technique to suit your own diabolical purposes ;) For now, let’s continue with an explanation of the functionality behind this dual-loop technique.

Technical Breakdown

Perhaps the most straightforward way to explain the dual-loop code is to break it down line-by-line via comments placed within the code itself:

// initiate the default wordpress loop as usual
<?php if (have_posts()) : while(have_posts()) : 

// set a count variable to increase with each loop
$i++; 

// test the variable modulus against a zero value
// odd values return true, even values return false
// see proceding discussion for more information
if(($i % 2) == 0) : 

// skip to next post if variable is an even number
$wp_query->next_post(); 

// display the post if variable is an odd number
else : the_post(); ?>

// open a division for the left column
<div id="left-column">

// display the title of the post
<h1><?php the_permalink(); ?></h1>

// display the post content
<?php the_content(); ?>

// close the division
</div>

// close the first if statement
<?php endif; 

// close the loop
endwhile; 

// if there are no posts that meet the criteria
else: ?>

// display some alternate content
<div>Alternate content</div>

// close the second if statement
<?php endif; ?>

// reset the count variable to zero
<?php $i = 0; 

// reset the loop
rewind_posts(); ?>

// the second loop is essentially the same as the first
// the only difference is that we are testing the count variable against a non-zero value to display only even numbers
<?php if (have_posts()) : while(have_posts()) : $i++; if(($i % 2) !== 0) : $wp_query->next_post(); else : the_post(); ?>

// and of course a unique div id for the right column
<div id="right-column">
<h1><?php the_permalink(); ?></h1>
<?php the_content(); ?>
</div>

<?php endif; endwhile; else: ?>
<div>Alternate content</div>
<?php endif; ?>

As for the crazy PHP modulus operator ( % ), suffice it to say that its purpose is to test the oddness or evenness of the $i variable. The modulus operator returns the numerical remainder resulting from the division of the $i variable by the specified number (“2” in this case). In the first loop, because all even post numbers are evenly divisible by two, the modulus is equal to zero and thus the evenly numbered posts are skipped until the next loop. In the second loop, the odd post numbers are not evenly divisible by two, resulting in a non-zero numerical remainder. Thus, in the second loop, we test that the modulus is not equal to zero, thereby skipping the oddly numbered posts. Perhaps this numerical pattern will help clarify the concept:

  • Post #1: $i = 1 [remainder of 1/2 = 1]
  • Post #2: $i = 2 [remainder of 2/2 = 0]
  • Post #3: $i = 3 [remainder of 3/2 = 1]
  • Post #4: $i = 4 [remainder of 4/2 = 0]
  • Post #5: $i = 5 [remainder of 5/2 = 1]
  • Post #6: $i = 6 [remainder of 6/2 = 0]
  • Post #7: $i = 7 [remainder of 7/2 = 1]
  • Post #8: $i = 8 [remainder of 8/2 = 0]

From this we can see how testing the modulus against zero (or non-zero) results in two groups of (odd and even) numbers. For more mental torture, here is more information on the PHP modulus operator. But enough of this boring math stuff — let’s move on, shall we?

Pure CSS Method

As the astute reader may have observed, displaying two columns of horizontally sequenced posts is also possible using a single, default WordPress loop and a little bit of CSS. Consider the following code:

<div id="container_division">
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

<div class="post-block">
<h1><?php the_permalink(); ?></h1>
<?php the_content(); ?>


</div>

<?php endwhile; else: ?>
<?php endif; ?>
</div>

With each post enclosed within a “post-block” division (i.e., <div class="post-block">), we can achieve a two-column post-display similar to that generated via the dual-loop method by declaring a width for each of the post blocks and then placing them within a fixed-width container division. Or, to express this idea visually:

[ Diagram: Two Columns of Horizontally Sequenced Divs ]

With all of the post-block divisions floated to the left, they will automatically “stack” according to the diagram. Here’s an example of CSS that would make this work:

div.post-block {
	width: 333px;
	float: left;
	clear: none;
	}
div#container_division {
	width: 700px;
	}

As useful as this “pure-CSS” technique happens to be, it is not as flexible as the dual-loop version. Independently functioning loops provide greater control over layout and thus greater design flexibility. For example, using two individual loops, the post columns need not appear side-by-side, but may be placed anywhere on the page.

Peace Out

That’s it for this Perishable Press tutorial. If you have any questions, concerns, or criticisms, please share them in the comments section for this article. As always, thanks for reading! :)

Jeff Starr
About the Author Jeff Starr = Web Developer. Security Specialist. WordPress Buff.
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58 responses
  1. Oh you are turning to ASCII art I see :p

    More seriously, I would have done the second method (Pure CSS) spontaneously. I mean, isn’t the first one too much complicated for achieving such a simple result ? :o

    Now, while it won’t do exactly the same result, I would like to underlign that Safari & Firefox already support the CSS3 multi-column specification. Yummy.

    Note: the pre formatting is perfect in my NetNewsWire.

  2. And now, what about some quick sketches instead of ascii art ? :)

  3. Jeff Starr

    There is nothing wrong a little ascii art! ;)

  4. Jeff Starr

    @Louis: Ah, but that’s the whole point — the result need be simple only if you are using the CSS-only method. As mentioned in the article, splitting the posts up via the dual-loop technique provides much more control over layout and additional functionality: category exclusion from one or both loops, limiting post count in either loop, and non-adjacent column positioning, for example, are all best handled at the PHP level. Don’t get me wrong, CSS is a great alternative if you merely need two columns of horizontally displayed posts. And, yes, that fruity new CSS3 multi-column business is looking extra-extra tasty (I can’t wait)!

  5. Oh! I LOVE it! I needed to see this. WP is virtually forcing me to delve deeper into PHP because I can’t code my way out of everything (ie your CSS technique vs your php technique) so these little tutorials are the best. Thanks a ton. :)

  6. Hi, thanks for the code. I got an error message after replacing the loop with your double code though (the first one):

    Parse error: syntax error, unexpected T_ENDWHILE in /html/wp-content/themes/classic2/index.php on line 53

  7. Jeff Starr

    Hi nomad1, I just double-checked the code on one of my sites and it works fine. One thing you need to watch for when replacing an existing loop is that you remember to delete all traces of it. This includes any closing endwhile and endif statements. If not removed when you add the new code, there will be redundant closing statements and you will get errors similar to the one in your comment.

  8. Jeff Starr

    @Erika: Always a pleasure! :)

  9. Thanks a lot Jeff, that was the reason. I have overlooked the last part of the loop!

  10. What if, instead of having the columns read from left to right, you wanted them to read from top to bottom then move over a column and proceed top to bottom, so:

    --post 1-- --post 3--
    --post 2-- --post 4--

    Maybe I’m over thinking this but would you do something like:

    count = 1

    BEGIN LOOP
    if count = 3 then

    end if

    COUNT++

    or is there a simpler way to do this with the rewind loop function and the query posts?

  11. Jeff Starr

    @nomad1: my pleasure — glad to hear you got it working :)

    @Michael: I would handle something like that with either CSS or via two loops for greater flexibility. I guess it all depends on page design. To use the dual-loop method above, you would simply omit the crazy modulus functionality and position the divs adjacently. There are other ways of doing this, of course — it all depends on your needs.

  12. I think a dual-loop method would be great, I’m just not sure how to start the second loop at the 3rd posts.

    By the way, I just discovered your web site today, and I’m really enjoying the articles, thanks.

    Michael

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