This event is signalled by _ft_pageSearch() in inc/fulltext.php when phrases are matched with the page content, handlers can use it to match their own page related content with the phrase as well.
The $event->data is passed the following array:
[ 'id' => $id, // string, page id 'phrase' => $phrase, //string, phrase to match with the content 'text' => rawWiki($id) //string, raw content of the wiki article ];
If the phrase matches the content, then $evt->result must be set to true. If already true, no further processing is needed.