Quite often, I use an ACF Post Object field to let the client chose a multiple number of items. That returns an array of post objects. If I want to get the ID for each of those post objects, you could loop over it. Or, let WP abstract that away with a little helper function. Enter
// $post_objects is our array of WP post objects $post_ids = wp_list_pluck($post_objects, 'ID');
We now have
$post_ids which only contains post ID’s. This is useful in a multitude of ways, like if you need to put them back into a
WP_Query or use those ID’s in some other way.
Array (  => 116  => 433  => 119 )
That can save a few lines of
foreach loops, can’t it. Cleaner code is always nice.