I have plan to link bbpress to events manager plugin.
The path is [bbpress]⇒[WP calendar]⇒[events manager].
The participants look at topic in bbpress at first.
Next he visits WP calendar and then events manager booking-form at last.

How to send the bbpress topic title which he visited
to the next next page(booking-form in events managaer)?

Do I have to use filter or actions in events manager?

The code ongoing

add_filter('events-manager-hook', 'bbpress_title', 20);
function bbpress_title($topic_title,$topic_id){

	global $my_global;  // previous-topic title and topic title in the events manager 	

	$topic_id = bbp_get_topic_id（）;
	$topic_title['title']=$topic_id -> ???;
	$my_global = get_topic_title();? ⇒　error!!

    }
return  $topic_title;
}

Or do you have any other plans?

[@sub0810 Participant 3 years, 9 months ago]

The resolution here

$_SESSION — Session variables

session