MediaWiki $wgUser to $this->getUser() and $context->getUser() not working - php

Question

I am learning Mediawiki and looking at some of the extensions.
Manual:$wgUser on mediawiki.org states the global variable $wgUser should not be used for new code.
Manual:RequestContext.php says the context object should be used instead, by using either $this->getUser() or $context->getUser().
However, when I try to use $this->getUser()->getName() in the extension for Who's Online I get the following error:
Fatal error: Using $this when not in object context in /home/ghsfhaco/public_html/wiki/extensions/WhosOnline/WhosOnlineHooks.php on line 19
And when I change it to $context->getUser()->getName() I get this error:
Fatal error: Call to a member function getUser() on null in /home/ghsfhaco/public_html/wiki/extensions/WhosOnline/WhosOnlineHooks.php on line 19
The full Extension:WhosOnline can be found at Mediawiki, but here's the specific page:
class WhosOnlineHooks {
// update online data
public static function onBeforePageDisplay() {
global $wgUser;
// write to DB (use master)
$dbw = wfGetDB( DB_MASTER );
$now = gmdate( 'YmdHis', time() );
// row to insert to table
$row = array(
'userid' => $wgUser->getId(),
'username' => $wgUser->getName(),
'timestamp' => $now
);
$method = __METHOD__;
$dbw->onTransactionIdle( function() use ( $dbw, $method, $row ) {
$dbw->upsert(
'online',
$row,
array( array( 'userid', 'username' ) ),
array( 'timestamp' => $row['timestamp'] ),
$method
);
} );
return true;
}
public static function onLoadExtensionSchemaUpdates( $updater ) {
$updater->addExtensionUpdate( array( 'addTable', 'online',
__DIR__ . '/whosonline.sql', true ) );
return true;
}
}
How exactly should it be done?
BTW, I'm using Mediawiki 1.28.0.

Answer 1

From the page you linked (Working with Request Contexts > When using hooks): If your hook provides an OutputPage as an argument make use of the context provided by it. BeforePageDisplay does provide an OutputPage, so just use its getUser() method.