On my latest Civi 5.37.2 the params array passed to hook_civicrm_pre
looks like:
Array
(
[hidden_custom] => 1
[hidden_custom_group_count] => Array
(
[] => 1
)
[custom_395_-1] => <-------- Spooky appdx
[custom_463_-1] => 1000 <-------- Spooky appdx
[...]
This happens when adding a new activity to a case. hook_civicrm_customPre
works in other cases but it is not fired here. So it seems, there is no hook to get a sane custom_<fieldid>
param prior saving to db.
-1
it's the autoincrement id in the customvalue table.