jquery计算总金额但不显示

I'm trying to build a small e-commerce website, and now that I just made my jquery program calculate items on cart, I was trying to calculate also the total amount of these items and print it next to the first one. So when I check out my source code then network then my js file in google chrome, I see that the amount was calculated correctly but it is not displayed. Here is my code:

My html span: (where to display the total amount):

<span id="total12"><?php echo $_SESSION['total'];?></span>

My addpanier.php file :

<?php 
    session_start();
    require 'connexion.php';
    require 'panier.php';
    $json=array('error' => true);
    $panier=new panier();
    try {
        $con1 = new myPDO();
    }
    catch (PDOException $e) {
        echo "<br/> Erreur: ".$e->getMessage()."<br/>" ;
        die() ;
    }
    if (isset($_GET['id'])) {
        $bdd = $con1->prepare("SELECT * FROM article a,promotion p WHERE a.id=p.id_article HAVING a.id=?") ;
        $bdd->bindValue(1,$_GET["id"]);
        $bdd->execute();
        $result = $bdd->fetch(PDO::FETCH_ASSOC);
        $tot2=0;
        if (empty($result)) {
            $json['message']="produit introuvable!";
        }else{
            $panier->add($result["id"]);
            $json['error']= false;
            if (isset($_SESSION['panier'])) {
                $tot=0;
                $tot=$result["prix"]*$_SESSION['panier'][$result["id"]];
                $b=$tot-$tot*($result["rabais"]/100)+$result["tax"];
                $tot2+=$b;
            }else{
                $tot=0;
                $tot=$result["prix"];
                $b=$tot-$tot*($result["rabais"]/100)+$result["tax"];
                $tot2+=$b;
            }
            $json['total1']=$tot2;
            $json['panier']= array_sum($_SESSION['panier']);
            $json['message']='produit bien ajoute a votre panier !';
        }
    }else{
        $json['message']="pas de produits a ajouter au panier";
    }
    echo json_encode($json);
?>

And my jquery file :

(function($){
    $('.addpanier').click(function(event){
        event.preventDefault();
        $.get($(this).attr('href'),{},function(data){
            if (data.error) {
                alert(data.message);
            }else{
                if(confirm(data.message + '. Voulez vous consulter votre panier?')){
                    location.href="product_summary.php";
                }else{
                    $('#panier12').empty().append(data.panier);
                    $('#total12').empty().append(data.total1);
                }
            }
        },'json');
        return false;
    });
})(jQuery);

use .html()

 $('#total12').html(data.total1);

thank you folks for your time, my error was in my selector, in fact i was checking if a session variable is existing right before where i should display my stuff Ibetter go to bed...(it is 2 a.m in Morocco). :D Thank you all !