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filter is not described

wp_dropdown_cats filter-hook . WP 2.1.0

Filters the taxonomy drop-down output.

Usage

add_filter( 'wp_dropdown_cats', 'filter_function_name_6767', 10, 2 );
function filter_function_name_6767( $output, $r ){
	// filter...

	return $output;
}
$output(string)
HTML output.
$r(array)
Arguments used to build the drop-down.

Where the hook is called

wp_dropdown_categories()
wp-includes/category-template.php 442
$output = apply_filters( 'wp_dropdown_cats', $output, $r );

Where the hook is used (in WP core)

Does not used.