The below PHP code is using the wordpress function wp_list_categories to display a list of categories. Have a look at the code:

<?php wp_list_categories( array(
    'orderby'    => 'count',
    'order'      => 'DESC',
    'show_count' => 1,
    'title_li'   => '',
    'number'     => 100
) ); ?>

Overall, this code will generate a list of categories ordered by post count, displaying the count for each category, and limiting the display to 100 categories.