PHP array_sum multi-dimensional - php

Question

I need to get the array_sum of $product['stars']; so I can use it to find the average. When I try to use it I am not using it on the array somehow? Also I believe this comes in as a string. Does it need to be converted to INT? Thanks so much for any ideas.
<?php
$categories = array();
while ($row_rsCategories = mysqli_fetch_assoc($res)) {
$product_array = array();
$product_array_query = mysqli_query($mysqli,"SELECT id, user_id, client_id, comments, stars FROM reviews WHERE user_id = '".$row_rsCategories['userId']."'");
while($product_array_fetch = mysqli_fetch_array($product_array_query)) {
$product_array[] = array("id"=>$product_array_fetch['user_id'],"comments"=>$product_array_fetch['comments'],"stars"=>$product_array_fetch['stars']);
}
$categories[] = array(
'id' => $row_rsCategories['userId'],
'name' => $row_rsCategories['usersName'],
'products' => $product_array,
);
}
foreach ($categories as $category) {
?>
<div class="col-md-4">
<div id = "user-square">
<div class="avatar">
<img src="<?php echo $avatarDir.$list['usersAvatar']; ?>" class="publicAvatar" />
</div>
<?php
echo $category['name']; ?> </br>
<?php foreach($category['products'] as $product) {
echo $product['stars']; ?> </br>
<?php }
?>

Answer 1

You could do it by combining array_sum with array_map:
$starsum = array_sum(array_map(function($x) { return $x['stars']; }, $product_array));
But you can also just calculate the sum while you're constructing the array of results:
$starsum = 0;
$rowcount = 0;
while($product_array_fetch = mysqli_fetch_array($product_array_query)) {
$product_array[] = array("id"=>$product_array_fetch['user_id'],"comments"=>$product_array_fetch['comments'],"stars"=>$product_array_fetch['stars']);
$starsum += $product_array_fetch['stars'];
$rowcount++;
}
$categories[] = array(
'id' => $row_rsCategories['userId'],
'name' => $row_rsCategories['usersName'],
'products' => $product_array,
'avgstars' => ($rowcount == 0) ? 0 : $starsum / $rowcount
);
There's no need to convert the values to integers, PHP will do that automatically when you use arithmetic functions on them.