Average post age in days per taxonomy term - wordpress

Question

I'm building some stats for a directory website and I got stuck calculating the average age of listings assigned to a particular listing type.
I figured out calculating listing age in days by ID:
$today = date( 'Y-m-d' );
$listing_date = get_the_date( 'Y-m-d', $id );
$diff = strtotime( $today ) - strtotime( $listing_date );
$age = round( $diff / 86400 );
I figured out how to pull listings assigned to a particular listing type by term ID:
$args = array(
'posts_per_page' => -1,
'fields' => 'ids',
'post_type' => 'listing',
'post_status' => 'publish',
'tax_query' => array(
array(
'taxonomy' => 'listing-type',
'field' => 'id',
'terms' => $id
)
)
);
$ids = get_posts( $args );
This gives me an array of IDs of all listings assigned to a particular listing type.
Now I need to calculate the total age in days for all those listings I retrieved IDs for.
I figured $cnt = count( $ids ); to get the total number of retrieved listings (IDs), but I can't figure out calculating the total age in days for those.

Answer 1

With a foreach loop :
<?php
// Your function to get the diff
function get_diff($id) {
$today = date( 'Y-m-d' );
$listing_date = get_the_date( 'Y-m-d', $id );
$diff = strtotime( $today ) - strtotime( $listing_date );
$age = round( $diff / 86400 );
return $age;
}
// We want to store all the diff
$diffs = [];
foreach($ids as $id) {
$diffs[] = get_diff($id);
}
// Get the average | We filter to remove empty values
$diffs = array_filter($diffs);
if(count($diffs)) {
echo $average = array_sum($diffs)/count($diffs);
}