In the example code:
https://www.advancedcustomfields.com/resources/acfsave_post/
Do you get the field data using your defined field name or the ACF field name?
$field = $_POST['acf']['field_abc123'];
That’s kind of ambiguous.
Before ACF, with a priority of <10 you must use $field = $_POST['acf']['field_abc123']; to get new values, the field name will not work. get_field(), with either the field name or the field key will return the old values.
With a priorty >10 all methods of getting the values will return the new value.
Interesting…
Here’s a question. If I call wp_insert_post() to create a new post and I use the ACF field names in the meta_input array, will that trigger ACF to do it’s thing?
What triggers ACF to save values is that $_POST[‘acf’] is set and has a value. I think that if you unset index before ACF (priority < 10) that ACF will do nothing at all, but I’m not 100% sure.
