posts_per_page is not working on my end

Question

It’s not working because the $posts_list variable is assigned the return value of get_posts() (i.e. $posts_list = get_posts( ... )), hence $posts_list is not actually an array of arguments, but instead, it’s either an array of posts or an empty array.

So to fix the problem, define the $posts_list like so:

$posts_list = array(
    'posts_per_page' => 6,
    'post_type'      => 'post',
    'post_status'    => 'publish',
    'paged'          => $i_paged
);