There is this function that is part of the plugin EasyDigitalDownlaods' plugin:

public function category_dropdown( $name = 'edd_categories', $selected = 0 ) {
    $categories = get_terms( 'download_category', apply_filters( 'edd_category_dropdown', array() ) );
    $options    = array();

    foreach ( $categories as $category ) {
        $options[ absint( $category->term_id ) ] = esc_html( $category->name );

    $category_labels = edd_get_taxonomy_labels( 'download_category' );
    $output          = $this->select( array(
        'name'             => $name,
        'selected'         => $selected,
        'options'          => $options,
        'show_option_all'  => sprintf( _x( 'All %s', 'plural: Example: "All Categories"', 'easy-digital-downloads' ), $category_labels['name'] ),
        'show_option_none' => false,
    ) );

    return $output;

I want to override it because it currently skip the empty categories due to the line 2:

$categories = get_terms( 'download_category', apply_filters( 'edd_category_dropdown', array() ) );

That needs to be changed to:

$categories = get_terms( 'download_category', apply_filters( 'edd_category_dropdown', array('hide_empty' => 0) ) );

I tried to add the following in my function.php but it seems that I don't understand how filtering works for this case:

function category_dropdown_unfiltered($array){
  $array = array('hide_empty' => 0);
  return $array;
add_filter( 'category_dropdown' , 'category_dropdown_unfiltered', 99, 1);
  • Oh I am filtering 'category_dropdown' instead of 'edd_category_dropdown'...
    – Niko
    Dec 19, 2023 at 12:57
  • you should write that as an answer rather than a comment, can't give you points for a comment!
    – Tom J Nowell
    Dec 19, 2023 at 14:25
  • I will give you these points, for taking the time to answer.
    – Niko
    Dec 19, 2023 at 16:33

1 Answer 1


This is the pattern for a filter.

Applying/using a filter on something:

$filtered_version = apply_filters( 'the name of the filter', $the_thing_being_filtered );

This is how you use a filter to modify something:

    'the name of the filter', 

function name_of_a_function_that_will_modify_the_thing_being_filtered( $the_thing_being_filtered ) {
    // modify $the_thing_being_filtered here
    return $the_thing_being_filtered;

So in your examples it did not work because category_dropdown is not the name of the filter, edd_category_dropdown is the name and they do not match so they do not work.

Order also matters, you can't add a filter to something after it has happened without some form or time travel. WP won't wait until all filters and actions/hooks are added then evaluate it at the end, that's not how PHP works.

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