I would like to output all apply_filters and do_action to give the user an overview of them.

If I use the Code

add_filter( 'wpErpOs_testFilter', 'wpErpOs_testFilter_callback', 10, 1 );
function wpErpOs_testFilter_callback( $testVar ) {
$testVar[] = "GM";
 return $testVar;
$testVar = array("VW", "Audi");
$testVar = apply_filters('wpErpOs_testFilter', $testVar);

then the hooks are displayed in

global $wp_filter;. 

If apply_filters is not called by add_filter, it does not appear in

global $wp_filter;;

How can I output all apply_filters and do_action, even those that are not called?

  • What do you mean by "How can I output all apply_filters"? Do you want to display all hooks? Or all registered filters/actions assigned to any hook? Commented Feb 21, 2019 at 19:39
  • I'd like to spend all the names of the hooks. Example: apply_filters('wpErpOs_testFilter', $testVar); ==> Name: wpErpOs_testFilter
    – Severin
    Commented Feb 22, 2019 at 12:23

1 Answer 1


apply_filters and do_action are NOT stored in $wp_filter, ONLY add_filter and add_action are stored in $wp_filter

When you call apply_filters or do_action, core WordPress loops through all of the registered filters or actions (added by add_filter and add_action), looking for any matching ones, and then executes the associated function.

The only difference being actions which are stored in the $wp_actions global var

These are the global vars available for hooks (actions/filters):

global $wp_filter, $wp_actions, $wp_current_filter;

$wp_actions - stores actions that have already been fired with the number of times it was fired, each time do_action is called this number is incremented.

You can look at the Query Monitor plugin which does handle tracking of hooks (actions/filters): https://github.com/johnbillion/query-monitor

Now with that said, one option you have that you can do, is to add your own action for the all action, and then collect and save the filters/actions that are ran yourself.

Here's some sites that talk about this: https://www.smashingmagazine.com/2012/02/inside-wordpress-actions-filters/

Here's example code of doing this: https://gist.github.com/bueltge/1000143


  • Tracing via the "all" hook only works for hooks called with add_filter() or add_action(). Did I understand this right?
    – Severin
    Commented Feb 22, 2019 at 21:14
  • The Plugin Query Monitor shows only hooks called with add_filter() or add_action().
    – Severin
    Commented Feb 22, 2019 at 21:27
  • @Severin no the code for the all hook in that example code will store in the db every single time apply_filters or do_action is called
    – sMyles
    Commented Feb 22, 2019 at 21:50

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