bbPress.org

After user searched key wards in one of the parent forums, I want to suggest topics that are a member of the parent forum.
For example,
Forum Top |- Forum B |-topic A
| |-topic F
|
|- Forum C |-topic A
|-topic Z

If an user now in Forum B searches topic A, only show topic A in Forum B, not Forum C’s topic A.

What I tried
First, I add this cord to my child theme’s function.php.
`function my_bbp_search_form(){
?>
<div class=”bbp-search-form”>

<?php bbp_get_template_part( ‘form’, ‘search’ ); ?>

</div>
<?php
}
add_action( ‘bbp_template_before_single_forum’, ‘my_bbp_search_form’ );`

Next, Add a field to the search form. I override form-search.php in my child theme’s /bbpress directory.

if ( bbp_allow_search() ) : ?>
<?php $forum_id = bbp_get_forum_id(); ?>
<div class="bbp-search-form">
	<form role="search" id="bbp-search-form" method="get" action="">
		<input type="text" value="" placeholder="Search <?php the_title(); ?> Topics"  name="s"/>
		<input type="hidden" name="forum_id" value="<?php echo $forum_id; ?>"/>
		<input type="submit"/>
	</form>
</div>

Finally, I filter the search query to only search a specific forum. I add this code to my functions.php.

<?php 
function my_bbp_filter_search_results( $r ){
	$s=htmlspecialchars($_GET['s'], ENT_QUOTES, 'UTF-8');
	$forum_id = htmlspecialchars($_GET['forum_id'], ENT_QUOTES, 'UTF-8');
if(isset($s)){
	$args=array(
	's'->$s,
	'post_parent'->$forum_id,
	);
        }
        return $r;
}
?>

However, it didn’t work so I want to know how to achieve this.

In addition, I challenged another way like this.

if(bbp_has_topics(array('s'->$s, 'post_parent'->$forum_id)))
        bbp_get_template_part('bbpress/loop', 'topics');

This code is that I edited above last additional functon “my_bbp_filter_search_results()” in function.php.
However, I can’t get search’s value(name=’s’) in the first place. I tried to use “echo $s;”, $s didn’t output the value. Where is the search results file of bbpress?

Please advise me. Thanks for reading.