Show categories in the sidebar

Hello people.

I wonder how do I display a list of a particular category in a widget? I tried put the code below into a text widget, but it did not work:

<ul class=”itens”>
<php wp_list_categories (‘child_of title_li = 2 & =’); >
</ ul>

I used this same code in the “category-blog” file, and it worked well! To view categories within a sidebar is necessary to create a custom widget? If yes, what is the procedure?

Remembering that I want to view the blog categories, and not posts.

Thanks in advance.