I am trying to add some code to be run when a post is updated. To get started I have added the following code to my functions.php:

function check_values($post_ID, $post_after, $post_before){
    echo 'Post ID:';

    echo 'Post Object AFTER update:';

    echo 'Post Object BEFORE update:';

add_action( 'post_updated', 'check_values', 10, 3 );

However, it doesn't seem to work. Nothing has changed when updating a post - nothing is echoed or dumped on screen.

Did I misunderstand something?

  • What is not working?
    – bravokeyl
    Aug 9, 2016 at 7:25
  • I guess it is supposed to show the echoes and var_dumps on screen as I update a post? It doesnt do that :-) Aug 9, 2016 at 7:26
  • Try writing logs. Sometimes due to the theme or any other reason data won't echo using var_dump. Apr 19 at 7:43

1 Answer 1


If it doesn't work you can try to use a wp_insert_post action:

function insert_post_hook($post_id, $post) {

    if ($post->post_date != $post->post_modified) {
        // This post is being updated!
    else {
        // This post is being created!
add_action( 'wp_insert_post', 'insert_post_hook', 10, 2 );

If you want to see the latest version you could enable revisions:

define('WP_POST_REVISIONS', 3 ); 

This will save a maximum of 3 revisions.

After enabling you can check the following:

$latest_revision = array_shift(wp_get_post_revisions($post->ID));
  • What I need to do, is to compare the old content of the post with the new content. I am adding notifications for things that has changed. That's why I wanted to use post_updated with $post_before. Can I do something similar with wp_insert_post? Aug 9, 2016 at 7:35
  • I think this can only be done with revisions, see modified answer.
    – Paul
    Aug 9, 2016 at 7:39
  • Thanks. But shouldn't the following approach echo on screen when saving a post? It doesn't do that either.. function insert_post_hook($post_id, $post) { echo 'The post was saved'; } add_action( 'wp_insert_post', 'insert_post_hook', 10, 2 ); Aug 9, 2016 at 7:41
  • 1
    You should probably add a exit; afterwards.
    – Paul
    Aug 9, 2016 at 7:42
  • Okay. I managed to get my post_revisions. However, the $latest_revision only contains the title, time and some more basic stuff. It doesnt contain all the fields that are shown in revisions in the editor. Can I get it all somehow? Aug 9, 2016 at 8:17

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