multiple values in an array for category__and does not work with WP_Query

Question

So I'm looping with WP_Query and here is my code:

$country_posts = new WP_Query(get_direct_children($continent_cats));
if ($country_posts->have_posts())  : while ($country_posts->have_posts()) : $country_posts->the_post();

the get_direct_children function:

function get_direct_children($cat_name) {
        if (gettype($cat_name) == 'string') : $category_id = get_cat_ID($cat_name);
        elseif (gettype($cat_name) == 'integer') : $category_id = $cat_name;
        endif;
        $args = array('parent'   => $category_id);
        $categories = get_categories($args);
        $cats = wp_list_pluck($categories,'cat_ID');
        $args = array (
              'category__and'                    => $cats
        );
        return $args;
    }

$country_posts->have_posts() returns true only if 1 category gets returned from get_direct_children. This happens when I turn off all the children of $continent_cats (which is a string by the way) except 1.

When only 1 child category is active:

var_dump(get_direct_children($continent_cats));

returns:

array(1) { ["category__and"]=> array(1) { [0]=> string(2) "72" } }

So yay this is what I want it to do. have_posts() is returning true and looping my 1 active subcategory. HOWEVER, when I enable another child category, have_posts() returns false(I think, it's just not posting any content).

So this same function:

var_dump(get_direct_children($continent_cats));

returns:

array(1) { ["category__and"]=> array(2) { [0]=> string(2) "72" [1]=> string(2) "71" } }

when I have 2 child categories active. Since this looks like correct syntax AND category__and is taking in the correct variable type, why doesn't it loop those 2 categories? Why does it not even loop 1 category?

Thanks

Answer 1

Changing:

$args = array (
              'category__and'                    => $cats
        );

to:

$args = array (
                  'category__in'                    => $cats
            );

Does the trick.