PHP echo with a function tag inside a HTML element

This is probably very easy for somebody with PHP skills and I think I’ve done-/seen it before but can’t remember where.

This is what I made.

function shmoo_time_switch_if_has_replies() {
	if ( bbp_get_topic_reply_count() ) {
		// topic_author + time_ago
		echo bbp_topic_author_display_name() . " " . bbp_get_topic_post_date( $topic_id = 0, $humanize = true, $gmt = false );

	}
	else {
		// topic_author + last_reply and his time_ago
		echo "something else";

	}
}

Now I would like to wrap that author_display_name in an HTML a href tag with another function that leads to the url (profile-page)