I'm in the process of writing a CDN plugin for WordPress and am trying to integrate it with the Advanced Custom Fields plugin. I need to filter the output of the "File" field type on the edit post screen so I can display the correct file size for an attachment not hosted locally.

Unfortunately, ACF doesn't provide a way to filter the output so I'm having to resort to completely overriding the ACF callback which outputs the field

To do this, I need to first remove the ACF callback from the action, then add my own. I'm not able to use remove_action() because the ACF callback is an object method and I cannot access the object variable

I don't want to use remove_all_actions() because it could potentially break other plugins hooking on to the action so I have come up with the following:

    global $wp_filter;

    if(isset($wp_filter['acf/create_field/type=file'])) {
        foreach($wp_filter['acf/create_field/type=file'] as $priority => $filters) {
            foreach($filters as $key => $filter) {
                if(is_array($filter['function']) && ($filter['function'][0] instanceof acf_field_file)) {

                    // If the function is an array, and the first part is an instance of the acf_field_file we have found what we're looking for

                    break 2;

    // Now add our own callback
    add_action('acf/create_field/type=file', array($this, 'create_file_field'));

There's just something about looping through the wp_filters global that I don't like. Is there a better way of doing this or am I going to have to stick with this ugly bit of code?

EDIT: I'd like to stress that this is NOT a support request/question for a 3rd party plugin (ACF). The plugin being used is not relevant to the question. The question, in it's most basic form, is how to remove a callback from an action which happens to be an object method where the object variable cannot be accessed

  • this would be a good question for ACF support, 3rd party plugins are off-topic here. – Milo Oct 29 '14 at 17:24
  • 1
    This isn't a support request for ACF. It's a general WordPress actions/filters question - The fact the plugin is ACF is completely irrelevant – Andy Oct 29 '14 at 17:27
  • have you tried remove_action with the classname in place of the object var? – Milo Oct 29 '14 at 17:43
  • It needs a variable to an object instance of a class rather than a class name. I did try just to be sure, but it didn't work – Andy Oct 29 '14 at 20:49