How to mark every 3rd post

My approach. No extra function, no filter. 🙂

<?php $GLOBALS['wpdb']->current_post = 0; ?>
<div <?php post_class( 0 === ++$GLOBALS['wpdb']->current_post % 3 ? 'third' : '' ); ?>>

Alternative:

<div <?php post_class( 0 === ++$GLOBALS['wpdb']->wpse_post_counter % 3 ? 'third' : '' ); ?>>

Related Posts:

  1. How to mark every 3rd post
  2. Count posts within a custom post type and specific taxonomy and terms?
  3. How to Display a List of Users Who Have Made at Least 1 Post?
  4. How to Display Network Post Count?
  5. How to cache a shortcode functions output?
  6. Count posts in category including child categories
  7. adding a custom css class to post
  8. Count singular post views automatically
  9. Set font size automatically according to number of words in post
  10. Network wide post count (WP Multisite)
  11. Odd/even class on article tag
  12. How to add padding between posts
  13. Redirect based on user post count
  14. Alternate custom content in the loop
  15. Show that current post is number X out of X
  16. Show the author’s count of total amount of posts assign to a custom taxonomy term
  17. Double count view in archive.php
  18. Count to how many categories a post belongs to
  19. Add Post Tags to Body Class
  20. Count total number across post types
  21. Count search results in heading
  22. How to hide first gallery for every post?
  23. Add a class to post title if a link ends with a certain extension
  24. Counter of posts ever posted – even deleted ones
  25. Display Published Posts Count for Certain Time Period
  26. How to make classes for posts?
  27. How can I get global $post to work for CPT and update user?
  28. Display Notification Bar on Header on Certain Post Count
  29. Show posts count for Categories and Tags in wp_nav_menu
  30. How to add category post count in main navigation menu [closed]
  31. Count number of posts of current month
  32. Add $values to post_class()
  33. Howto show comment count by post in post?
  34. Counter is skipping post when I still want it visible [closed]
  35. Every second post different class in blog view
  36. Count several post tags
  37. Get post number both in the loop and in the post
  38. How do I insert a after every 5 posts in a WordPress Loop that infinitely loads posts?
  39. Count the number of a post types associated with another post type
  40. How can I add a class to particular paragraphs in my post?
  41. Microformats in a single post – layout conflict
  42. Echo the number of posts being displayed
  43. wordpress add field to post_class
  44. Display amount of pending posts in back/front end
  45. Count user posts and store the number for later use
  46. why the posts queried from sql is more than those showed on the page?
  47. Count the total views of all user posts published
  48. Author post count in category
  49. Set post title font size automatically according to number of words in post title
  50. Show post count in custom taxonomy page
  51. Count singular post views automatically
  52. How to count posts in tags within time limit
  53. Display Custom Post Category Count & WordPress Category Count Using Shortcode
  54. Counting Posts by Category
  55. Display number of post published every day
  56. Retrieve posts inside foundation tabs and tab-content split by 3 per row
  57. Alternative content between posts no repetition
  58. count_posts to a standalone link
  59. How to control Post view count incresing in sidebar widget posts too?
  60. Add a minimum word count to Excerpt (and how to force Excerpt as a rule for WyPiekacz)
  61. How to limit the number of posts a user can publish based on user type
  62. ho can I get the number of the current post instead of the post id?
  63. post_count not working
  64. Adding Count Post in Page
  65. Count words for all posts by all authors
  66. Word count for all posts of all authors
  67. Display post count on archive page in reverse order
  68. Change Posts per page count
  69. Can I force a metabox to be in one column?
  70. Post publish only hook?
  71. Restrict access to post if it is currently being edited
  72. Query only Posts from Both of Two Category?
  73. wp_update_term is always launched after wp_insert_term
  74. why does HTML Tag not working in Post and Page
  75. Posts are being redirected to xampp home page
  76. Can I lock a post in position, so it always appears on the homepage?
  77. Custom post preview without saving
  78. How do I correctly set up a WP-Query to only show upcoming event-posts?
  79. How to Restrict Previous & Next Post Link to Posts of Same Category?
  80. How to get a post’s details by shortcode?
  81. Posts on a Page using functions.php
  82. Why is my custom template not showing anything?
  83. $_GET parametters not working in an specific template
  84. How to get all inline images in post content? [duplicate]
  85. Link post images to post
  86. Rewriting blog permalinks
  87. How to exclude native lazy loading from first image in post content?
  88. WordPress 5: prevent link from displaying page title instead of URL
  89. Customizing a new page used for blog posts with Avada theme
  90. Repeating post how to solve this
  91. Showing content from WordPress ruins page CSS using WP_Query, without, content does not show
  92. Show a Category Specific Info Box
  93. post content includes and seo vs. duplicate content
  94. Posts don’t appear on the Blog page
  95. Display the first post’s comments of category in comments.php template
  96. On the post list, how do you show different text to the main content?
  97. Showing Unpublished Posts to Logged-out Users?
  98. Need All the posts with id, title and date [closed]
  99. List posts related to category on a div [closed]
  100. How to get only post=’product’
techhipbettruvabetnorabahisbahis forumueduseduedueduedueduseduseduseduedus