Usually, when I’m doing something like this with repeater fields I don’t actually use ACF functions or try to work directly with the values in $_POST.
Here’s an example of something I’d do, I do this because I know how ACF stores data and it’s just easier and faster to work with native WP functions for me.
post_updating_callback($post_id) {
$repeater = 'my_repeater'; // the field name of the repeater field
$subfield1 = 'subfield_1'; // the field I want to get
$subfield2 = 'subfield_2'; // the field I want to set
// get the number of rows in the repeater
$count = intval(get_post_meta($post_id, $repeater, true);
// loop through the rows
for (i=0; $i<$count; $i++) {
$get_field = $repeater.'_'.$i.'_'.$subfield1;
$set_field = $repeater.'_'.$i.'_'.$subfield2;
$value = get_post_meta($post_id, $get_field, true);
// do whatever I need to calculate the value to set
// $new_value will hold the value to set
update_post_meta($post_id, $set_field, $new_value);
}
}
Hope this helps.
