We just started getting a strange php error:
PHP Notice
Undefined variable: closest_parentIt happened in 2 places, when editing an asset builder, and just now when I was adding a trigger.
It has never happened before.
It happened in 2 places, when editing an asset builder, and just now when I was adding a trigger.
It has never happened before.
Sounds like mismatched versions of the CMS package and the Core code, potentially.
Again, something that could be potentially fixed by upgrading the entire codebase to v3.12.3. 
We would need the full error, with file/line number to do a proper debug. You can enable higher debugging levels by enabling the additional debug details on the System Configuration screen.
This was a typo bug found in Search Manager’s “tree-location weighting” code, in version 3.12.0 of Matrix (bug #2023). You would probably need to arrange for an update to a later version (eg. 3.12.3 as Avi suggested) to alleviate the problem.
Looks like the case. We are getting upgraded to 3.14 on Monday.
16:15:02 - 01 May
User: Root User (12)
Level: PHP Notice
(/packages/search/search_manager/search_manager.inc:1462) - Undefined variable: closest_parent