How to show the number of post of a category in sidebar

If you use
$category = get_category($categoryid)
you will get details about the category and use $category[‘category_count’] to get the number of posts under that.

A function exists to do just that…

wp_list_categories(); IIRC… ??

If using the Category Widget just check the Show post counts checkbox.

You can also add the template tag, wp_list_categories(), to a theme’s sidebar.php, and use the show_count=1 argument.

Related:
Stepping Into Template Tags
Stepping Into Templates
Template Hierarchy

awesome, such an easy fix, thank you guys!