This is an expansion of my comment on OP:
function is_forum_subscribed($user_ID) {
if($user_ID)
{
$useremail = $this->get_userdata($user_ID, 'user_email');
$list = get_option("mf_forum_subscribers_".$this->current_forum, array());
if(in_array($useremail, $list))
return true;
}
return false;
}
}
You can call this function like this, instead:
is_forum_subscribed($player->ID);