WP add_filter/custom query

//following is in functions.php (inside the theme folder)

if (isset($_GET['sort'])) {
$sort = $_GET['sort'];
}

add_filter('posts_join', 'votes_join');
add_filter('posts_where', 'votes_where');
add_filter('posts_orderby', 'votes_orderby');

function votes_join($join)
{
        global $sort;
        if (is_front_page() && !empty($sort)) {
           if ($sort == 1 || $sort == 2){
              $join = "LEFT JOIN wp_xbhuui_wpv_voting ON wp_xbhuui_posts.ID = wp_xbhuui_wpv_voting.post_id";
           }
        }

        return $join;
}

function votes_where($where)
{
        global $sort;
        if (is_front_page() && !empty($sort)) {

        if ($sort == 1) {
          $where .= "AND (post_date > DATE_SUB(NOW(), INTERVAL 1 DAY) OR wp_xbhuui_posts.ID = '31' OR wp_xbhuui_posts.ID = '2' OR wp_xbhuui_posts.ID = '5' OR wp_xbhuui_posts.ID = '1018')";
        }
        elseif ($sort == 2) {
          $where .= "AND (post_date > DATE_SUB(NOW(), INTERVAL 7 DAY) OR wp_xbhuui_posts.ID = '31' OR wp_xbhuui_posts.ID = '2' OR wp_xbhuui_posts.ID = '5' OR wp_xbhuui_posts.ID = '1018')";
        }
        else {
        //no sort selected, do nothing
        }}
        return $where;
}

function votes_orderby ($orderby)
{
        global $sort;
        if (is_front_page() && !empty($sort)) {

        if ($sort == 1 || $sort == 2){
        $orderby = "vote_count DESC";
        }
        }
        return $orderby;
}

//following is in top of index.php template file
global $sort;
$sort = 1;