function HTFV_Change($topic = 0, $hide_topic = false)
{
    global $user_info, $smcFunc;
 
    // Abort if we are not supposed to be here!
    if (empty($user_info['id']) || empty($topic))
        fatal_lang_error('no_topic_id', false);
    
    // Get the board number that this topic resides in:
    $request = $smcFunc['db_query']('', '
        SELECT id_board
        FROM {db_prefix}topics
        WHERE id_topic IN ({int:id_topic})',
        array(
            'id_topic' => $topic = (int) $topic,
        )
    );
    list($board) = $smcFunc['db_fetch_row']($request);
    $smcFunc['db_free_result']($request);
 
    // Remove any existing entries for this topic:
    $smcFunc['db_query']('', '
        DELETE FROM {db_prefix}hide_topics
        WHERE id_member = {int:id_member}
            AND id_topic = {int:id_topic}',
        array(
            'id_member' => (int) $user_info['id'],
            'id_topic' => (int) $topic,
        )
    );
 
    // Are we being requested to hide the specified topic?
    if ($hide_topic)
    {
        // Can't do anything if the board ID is empty, either....
        $user = (int) $user_info['id'];
        if (empty($board))
            continue;
 
        // Insert the row into the hide_topics table:
        $smcFunc['db_insert']('insert',
            '{db_prefix}hide_topics',
            array('id_member' => 'int', 'id_topic' => 'int', 'id_board' => 'int'),
            array($user, $topic, (int) $board),
            array('id_member', 'id_topic', 'id_board')
        );
    }
 
    // Force recache of the hidden topics for this user, then go to the board:
    unset($_SESSION['hide_topics']);
    return $board;
}