Insert Commas into ACF number field

Question

I am displaying numbers (non currency) via an advance custom field of paid_attendance - however by default number fields in ACF do not include commas or decimals etc.

I would like for commas to be included when the numbers from paid_attendance are output to the user on the front end. I am aware this can be done through the template file but I need to make it global via functions.php. I am probably way off, but below is the code I put together. Any help would be greatly appreciated.

// Return number with commas
function fix_number( $wpdb ) {
$number = get_field('paid_attendance');
number_format($number)."<br>";
}
add_action('fix_number');

EDIT Below is the fix and I have now got it working. Clearly and as Rick mentioned I was not using hooks properly. After reading deeper into the ACF docs and consulting other users on their forum, I was able to do what I need.

add_filter('acf/format_value/name=paid_attendance', 'fix_number', 20, 3);
function fix_number($value, $post_id, $field) {
  $value = number_format($value);
  return $value;
}

Answer 1

You need to 'hook' your function to a valid hook. Your add_action call is not doing anything, because it is not a proper call to a hook.. See the docs https://developer.wordpress.org/reference/functions/add_action/ for add_action.

Your function is the second parameter of the add_action hook. The first parameter is 'where' to hook into WordPress. If you want to modify the post content, then hook into the_content (see https://developer.wordpress.org/reference/hooks/the_content/ ).

But, then you need to parse the_content to find a number to format. The the_content hook works on the entire post (or page) content, so your function won't work.

So, not sure that you can do what you want. But if you are going to use hooks, then you need to learn how they work. The above links are a starting point.