Why isn't this Wordpress query sorting properly - wordpress

Question

I have a custom post_type called special_listing which contains a custom field called listing_index. A special_listing with a listing_index of 20, should appear before one with an index of 15, then 10, and so on. However this doesn't appear to be working and listings appear in whatever order they choose.
I'm not a PHP or Wordpress guy, I mainly deal with ASP.Net and C# so this is a bit confusing for me. Is there some simple mistake I'm making?
Function:
// Get the first $count listings with the highest indices for a given $region_slug:
function get_listings($region_slug, $count) {
$args = array(
'post_type' => 'special_listing',
'meta_key' => 'listing_region_slug',
'meta_value' => $region_slug
);
$posts = get_posts($args);
sort_array_on_field($posts, 'listing_index', 'DESC');
truncate_array($posts, $count);
return $posts;
}
View:
<?php
$listings = get_listings(get_microsite_slug() . '-microsite-home-featured', 4);
$i = 0;
if (sizeof($listings) > 0) : while ($i < sizeof($listings)) : $listing = $listings[$i]; // Loop and set current listing
?>
<section>
<a href="<?php echo $listing->destination; ?>">
<h3><?php echo $listing->post_title; ?></h3>
<p><?php echo $listing->post_content; ?></p>
</a>
</section>
<?php $i++; ?>
<?php endwhile; ?>
<?php endif; ?>
My attempt:
I don't know how to return the listing_index value
function get_sorted_listings($region_slug, $count){
$args = array(
'post_type' => 'kodakalaris_listing',
'meta_query' => array(
'relation' => 'AND',
array (
'key' => 'listing_region_slug',
'value' => $region_slug
),
array (
'key' => 'listing_index',
'value' => ''
),
orderby: 'listing_index',
order: 'DESC'
)
);
$posts = get_posts($args);
truncate_array($posts, $count);
return $posts;
}
Update
Trying a new way and it now pulls the content in by the published date. Still not ordering by listing_index, but at least it's not completely random either. I began looking to meta_query. Won't this only return a result with a single value? I've also tried out this other SO answer, but I find it's implementation confusing.
<?php
$args = array(
'post_type' => 'kodakalaris_listing',
'meta_key' => 'listing_region_slug',
'meta_value' => get_microsite_slug() . '-microsite-home-featured',
'posts_per_page' => 4,
'order' => 'DESC',
'orderby' => 'listing_index'
);
$listings = new WP_Query($args);
if ($listings->have_posts()) : while ($listings->have_posts()) : $listings->the_post();
?>
...
...
<?php
endwhile;
endif;
?>

Answer 1

You don't need to sort after you query. WP_Query has orderby parameters:
function get_listings($region_slug, $count) {
$args = array(
'post_type' => 'special_listing',
'meta_key' => 'listing_region_slug',
'meta_value' => $region_slug,
'orderby' => 'meta_value_num'
);
$posts = new WP_Query($args);
return $posts;
}
You'll then want to use The Loop rather than a foreach loop, in your view.

Answer 2

So I was able to figure this out after reading this article, but basically assigning a name to each meta_query array allows you to call which one should take priority when using orderby.
$args = array(
'post_type' => 'special_listing',
'posts_per_page' => 4,
'orderby' => 'index_clause',
'meta_query' => array (
'site_clause' => array (
'key' => 'listing_region_slug',
'value' => get_microsite_slug() . '-microsite-home-featured'
),
'index_clause' => array (
'key' => 'listing_index',
)
)
);

Answer 3

Change the function to :
<?php
// Get the first $count listings with the highest indices for a given $region_slug:
function get_listings($region_slug, $count) {
$args = array(
'post_type' => 'special_listing',
'orderby' => 'listing_index',
'order' => 'DESC',
'meta_key' => 'listing_region_slug',
'meta_value' => $region_slug
);
$posts = get_posts($args);
return $posts;
}