javascript - 我的功能会继续在购物车中添加产品，即使它存在并且没有显示任何警报。我该如何避免这个问题？

Question

我的功能会继续在购物车中添加产品，即使它存在并且没有显示任何警报。我该如何避免这个问题？

function cart(){       
               if(isset($_POST['cart'])){
                require('inc/connect.php');
        
                $ip = getIp();
                $product_id = filter_var($_POST['productId'],FILTER_VALIDATE_INT);
                $quatity    = filter_var($_POST['quantity'],FILTER_VALIDATE_INT);
                $size       = filter_var($_POST['size'],FILTER_SANITIZE_STRING);
                
                $a = "SELECT * FROM cart WHERE productid = '$product_id' AND ipAddress='$ip' ";
                $result = $con->prepare($a);
                $checkcart = $result->execute();
                
                if($checkcart == 1){
        
                    echo"<script>alert('Product Added Already</script>";
                    echo"<script>window.open('index.php','_self')</script>";
                }else{
                     $case = "INSERT INTO cart(productid,quantity,size,ipAddress)VALUES(?,?,?,?)";
                    $stmt = $con->prepare($case);     
                    $check = $stmt->execute(array($product_id,$quatity,$size,$ip));
        
                    if(!$check){
        
                        echo"<script>alert('Sorry, Product not added please try Again !)</script>";
                        echo"<script>window.open('index.php','_self')</script>";
        
                    }else{
                        echo"<script>alert('Product Added to cart</script>";
                        echo"<script>window.open('index.php','_self')</script>";
                    }
                }
                         
                }    
               
           }

标签： javascriptphp