Group search results by category

Add in the search parameter to your query:

$search_filters = array(
   'post_type' => 'page', // Doorzoekt alle post types
   's' => $keyword // show only posts that meet the current search query
);

And above that you should just be able to grab the keyword right from your querystring like so:

$keyword = $_GET['s'];

There’s also a WordPress native function that grabs your current search query which might be better to use than grabbing it manually from the querystring:

$keyword = get_search_query();