How to insert an ad between posts in WordPress

Does your project call for you to insert an ad, graphic, or some other type of content between posts? If so, there’s a very easy solution.

A typical loop looks like this, taken from the twentyfourteen theme:

if ( have_posts() ) :
  while ( have_posts() ) : the_post();
    get_template_part( 'content', get_post_format() );
  endwhile;
else :
  get_template_part( 'content', 'none' );
endif;

The trick is using the modulus operator (%), which gives you the remainder after dividing by a number (think back to elementary school).

You need to set a counter variable ($counter = 1) and increment it by one after each post ($counter++). Wherever the remainder is equal to 0, we display our custom code. Otherwise, display the regular post.

In this example, I’m inserting some code for every 4th post:

php
if ( $counter % 4 == 0 ):
  // your ad code here
else:
  // regular post
endif;
?>

Now with everything together:

php
if ( have_posts() ) :
  $counter = 1; //initialize the counter
  while ( have_posts() ) : the_post();
    if ( $counter % 4 == 0 ):
        // your ad code here
    else:
       get_template_part( 'content', get_post_format() );
    endif;

    $counter++; //increment by 1
  endwhile;
...
endif;
?>

Every theme is different, so don’t copy and paste this code directly into your theme file.