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I need to add the "All Categories" item to the default WP categories widget.

I can see that there's a filter that I can hook into in the core (line 485 default-widgets.php).

wp_list_categories(apply_filters('widget_categories_args', $cat_args)); 

I've written the following function, but I must have something wrong as it's not adding the all categories item to the list.

// Add "All Categories" to categories widget
function add_all_categories_to_widget($cat_args) {
    $cat_args['show_option_all'] = 'yes';
    return $cat_args;
add_filter('widget_categories_dropdown_args', 'add_all_categories_to_widget');

Can anyone fill me in on what I've got wrong?


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Sorry, I was just hooking into the wrong filter. My add_filter should have hooked into widget_categories_args not widget_categories_dropdown_args.

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