Manual:$wgHooks

Extensions: $wgHooks
Global list of hooks.
Introduced in version:	1.4.0 (r6405)
Removed in version:	Still in use
Allowed values:	See details
Default value:	`[]`
Other settings: Alphabetical \| By function

Details

Global list of hooks. It is an array of arrays: it specifies for every event an array of functions to be called.

In MW 1.40, the use of $wgHooks after initialisation was deprecated (T331602). Use HookContainer::register and HookContainer::scopedRegister instead.

Add a hook by doing:

$wgHooks['event_name'][]='function';

or:

$wgHooks['event_name'][]=array('function',$data);

or:

$wgHooks['event_name'][]=array($object,'method');

or:

$wgHooks['event_name'][]=$object;

In the last case, the callback is expected to be a method in $object of the same name as the event preceded by "on", e.g. "onUnknownAction"

Hooks are called when events happen, where a hook is a PHP function, and an event is an abstract concept.