Dropdown menu of categories with Walker.

wp-dropdown-menu-of-categories.php

<?php

	# Walker Class
	class my_Walker_CategoryDropdown extends Walker_CategoryDropdown {
	
		function start_el(&$output, $category, $depth, $args) {
			
			$pad = str_repeat('&nbsp;', $depth * 3);
	
			$cat_name = apply_filters('list_cats', $category->name, $category);
			
			$output .= "\t<option class=\"level-$depth\" value=\"".$category->slug."\"";
			
			// Checks if the slug of the category is equal to the selected category
			if ( $category->slug == $args['selected'] )
				$output .= ' selected="selected"';
			$output .= '>';
			$output .= $pad.$cat_name;
			
			if ( $args['show_count'] )
				$output .= '&nbsp;&nbsp;('. $category->count .')';
			
			if ( $args['show_last_update'] ) {
				$format = 'Y-m-d';
				$output .= '&nbsp;&nbsp;' . gmdate($format, $category->last_update_timestamp);
			}
	
			$output .= "</option>\n";
	
		}
	}
	
	# Arguments
	$args = array(
		'show_option_all'    => '',
		'show_option_none'   => '',
		'orderby'            => 'ID', 
		'order'              => 'ASC',
		'show_count'         => 0,
		'hide_empty'         => 1, 
		'child_of'           => 0,
		'exclude'            => '',
		'echo'               => 1,
		'selected'           => '',
		'hierarchical'       => 0, 
		'name'               => '',
		'id'                 => '',
		'class'              => 'postform',
		'depth'              => 0,
		'tab_index'          => 0,
		'taxonomy'           => 'category',
		'hide_if_empty'      => false,
	        'walker'             => new my_Walker_CategoryDropdown
	);
	
	# Dropdown
	wp_dropdown_categories( $args );

?>