How to improve Ajax pagination in WordPress

The big problem with the archive pagination in WordPress is that it’s based on a fixed number of posts. So when you open a homepage of a busy news site it shows last 10 articles. If you go to the second page it shows next 10 articles and so on.

The issue starts when you remain on the homepage for a bit longer. If a new article was published in the meantime going to the second page will move the last article from the first page to the second page of the archive.

Here’s a video demonstrating the issue on a website with a “Load More Posts” button. The Ajax call which loads these posts is simply using standard WordPress paged archive. So the “AFC East Notes: Allen, Van Ginkel, Patriots” post appears the second time as a new blog post had been published before we hit the button:

Link

Clicking "Load More Posts" loads the same post again

The solution here is to switch “Load More” entries to count by date. So instead of the standard:

/page/2

We are using:

/page/2?load_after=2023-06-05-12:52:33

Here’s what the code looks like:

/**
 * Template function:
 * Add ?load_after to the link, using the date of the last post in the loop
 */
function fv_archive_paging_load_after( $link ) {
  global $post;

  // Skip the search pages
  if ( stripos( $link, '?s=' ) !== false || stripos( $link, '/search/' ) !== false ) {
    return $link;
  }

  $link = remove_query_arg( 'load_after', $link );
  $link = remove_query_arg( 'load_before', $link );

  return add_query_arg( 'load_after', str_replace( ' ', '-', $post->post_date ), $link );
}

function fv_archive_paging_load_after_cb( $next_link ) {
  $next_link = preg_replace_callback(
    '~href="(.*?)"~',
    function( $match ) {
      return str_replace(
        $match[1],
        fv_archive_paging_load_after( html_entity_decode( $match[1] ) ),
        $match[0]
      );
    },
    $next_link
  );

  return $next_link;
}

/**
 * Respect ?load_after and ?load_before URL query arguments
 */
add_action(
  'pre_get_posts',
  function( $query ) {

    if ( ! $query->is_main_query() ) {
      return;
    }

    // Get rid of standard paging variables, but save them for later
    // as we need to retain the original pagination number of be able to figure out
    // if there are more pages of content
    if ( ! empty( $_GET['load_after'] ) || ! empty( $_GET['load_before'] ) ) {
      $query->set( 'fv_revert_paged', $query->get( 'paged' ) );

      $query->set( 'paged', false );
    }

    if ( ! empty( $_GET['load_after'] ) ) {
      if ( preg_match( '~([0-9]{4}-[0-9]{2}-[0-9]{2})-([0-9]{2}:[0-9]{2}:[0-9]{2})~', $_GET['load_after'], $match ) ) {
        $query->set(
          'date_query',
          array(
            'before' => $match[1] . ' ' . $match[2]
          )
        );
      }
    } else if ( ! empty( $_GET['load_before'] ) ) {
      if ( preg_match( '~([0-9]{4}-[0-9]{2}-[0-9]{2})-([0-9]{2}:[0-9]{2}:[0-9]{2})~', $_GET['load_before'], $match ) ) {
        $query->set(
          'date_query',
          array(
            'after' => $match[1] . ' ' . $match[2]
          )
        );

        // Later we have to flip the order of the posts loaded - see the_posts filter
        $query->set( 'order', 'ASC' );
        $query->query_vars['fv_revert_order'] = 'DSC';
      }
    }
  }
);

/**
 * Revert order of posts if we loaded posts using ?load_before
 */
add_filter(
  'the_posts',
  function( $posts, $wp_query ) {
    if ( $wp_query->get( 'fv_revert_order' ) ) {
      $posts = array_reverse( $posts );
    }
    return $posts;
  },
  10,
  2
);

/**
 * Put the original paging back to make sure pagination controls sense the last page of posts properly
 * Also set the max_num_page to indicated there are more posts
 */
add_action(
  'wp_head',
  function() {
    global $paged, $wp_query;
    if ( $wp_query->get( 'fv_revert_paged' ) ) {
      $paged = $wp_query->get( 'fv_revert_paged' );

      $wp_query->max_num_pages = $paged + 1;
    }
  }
);

/**
 * Since WordPress fails to detect a paged URL and adds the trailing slash we need to ensure it understands it is indeed paged and only use trailing slash if permalinks require that
 */
add_filter(
  'redirect_canonical',
  function( $redirect_url ) {

    if ( get_query_var( 'fv_revert_paged' ) > 0 ) {
      $redirect = wp_parse_url( $redirect_url );
      // Replace the URL path with the URL path with the traling slash removed and then added if needed
      $redirect_url = str_replace( $redirect['path'], user_trailingslashit( untrailingslashit( $redirect['path'] ), 'paged' ), $redirect_url );
    }

    return $redirect_url;
  }
);

Just add that code to your theme functions.php file.

To finally use this in your template you have to wrap your get_next_posts_link() call in fv_archive_paging_load_after_cb():

$next = get_next_posts_link();
if ( $next ) {
  echo fv_archive_paging_load_after_cb( $next );
}

Unfortunately get_next_posts_link() does not come with any filter for the href="..", see WordPress core code. So you really need to put that into your template.

Overall this is a bit of work to be done and we wish it would be a simple plugin which could be used on any website. Well, at least with the traditional WordPress themes and not Block or Elementor themes. These might need a slightly different solution.

Martin Viceník

Martin graduated as an engineer in Computer Science from Slovak Technical University in Bratislava. He grew up in Liptovský Mikuláš in northern Slovakia next to the beautiful Tatra mountains. He is the developer behind our FV Player.