Search bar for page that searches only particular page IDs

Question

How can I create a search bar for a page that searches only in particular page IDs? This shouldn't affect the search bar on other pages.

I tried the following:

 add_filter( 'pre_get_posts', 'pregetposts_forspecificpage' );

    function pregetposts_forspecificpage($query){
       if ($query->is_search) {
       $query->set('post_type', 'page');
       $query->set('post__in', array(22103,22121));
       }
       return $query;
    }

But this affects search bars used on other pages.

Answer 1

You can try to modify your filter like this

function pregetposts_forspecificpage($query){
   if(!is_admin() && $query->is_main_query() && is_search())
   {
     $query->set('post_type', 'page');
     $query->set('post__in', array(22103,22121));
   }
}

Edit : added !is_admin() because we only want to alter the query in the front. $query->is_main_query() to be sure that we are altering the main query. Replaced $query->is_search by is_search()

Also, you don't have to return the $query.