Why am I getting HTTP: 500 Internal Server Error when I am trying to use after_retrieve?

I am trying to use logic hook 'after_retrieve', but I keep getting a 500 Internal Server Error when it is trying to load records into the subpanel.

It happens whether I have something called by after_retrieve or even just set it as an empty array.

I even tried 'after_fetch_query', but that never runs anything.

$hook_array{'after_retrieve'] = Array();
$hook_array['after_retrieve'] =  Array(11, "Check Whether to Highlight Title","custom/Resources/logic_hooks/Courses_Logic_Hooks.php", "Courses_Logic_Hooks", "setAlertField",);