无法将相同的产品添加到购物车

Question

I have created an add to cart code using session and jquery. It's almost done but I am getting two issues.

1) When I refresh the page, I am getting error

Notice: Undefined index: quantity in C:\xampp\htdocs\add-to-cart\ajax_cart.php on line 5

2) I am able to add the product to the cart but If I add the same product two times then I am getting the error.

 Notice: Undefined index: 250.00 in C:\xampp\htdocs\add-to-cart\ajax_cart.php on line 30
 Notice: Undefined offset: 1 in C:\xampp\htdocs\add-to-cart\ajax_cart.php on line 31

There is some issue with else part (might be the price).

else{
    $_SESSION['product_cart'][$product_id][$product_price] = $_SESSION['product_cart'][$product_id][$product_price] + ($product_price*$quantity);
    $_SESSION['product_cart'][$product_id][$quantity] = $_SESSION['product_cart'][$product_id][$quantity]+$quantity;
    }

AJAX function to call the ajax_cart.php

function add_cart(p_id=""){
    var quantity = $(".quantity"+p_id).val();
    $.ajax({
        type:"post",
        url:"ajax_cart.php",
        data:{action:'add',p_id:p_id,quantity:quantity},
        success:function(result){
            $('.cart_data').html(result);
        }
    });
}

Add to Cart

$action = $_POST['action'];
 $p_id   = trim($_POST['p_id']);
 $quantity = $_POST['quantity'];
if($action == 'add'){
     if(!empty($p_id)){
           $query = "SELECT product_id,product_title,product_price,product_image FROM product WHERE product_id=?";
            if ($stmt = $conn->prepare($query)) {
                $stmt->bind_param("i", $p_id);
                $stmt->execute();
                $stmt->bind_result($product_id, $product_title,$product_price, $product_image);
                $stmt->fetch();
              }

             $product = array(
                "p_id"=>$product_id,
                "title"=>$product_title,
                "price"=>$product_price*$quantity,
                "image"=>$product_image,
                "quantity"=>$quantity
             );
        if(isset($_SESSION['product_cart']) && !empty($_SESSION['product_cart']))
        {
            if(!array_key_exists($product_id,$_SESSION['product_cart']))
            {
                $_SESSION['product_cart'][$product_id] = $product;
            }
            else{
                $_SESSION['product_cart'][$product_id][$product_price] = $_SESSION['product_cart'][$product_id][$product_price] + ($product_price*$quantity);
                $_SESSION['product_cart'][$product_id][$quantity] = $_SESSION['product_cart'][$product_id][$quantity]+$quantity;
            }       
        }
        else{
          $_SESSION['product_cart'][$product_id] = $product;
        }
    }   
}

Answer 1

use the else part as below

else{
            $_SESSION['product_cart'][$product_id]['price'] += ($product_price*$quantity);
            $_SESSION['product_cart'][$product_id]['quantity'] += $quantity;
        }   

and add below code

if(!isset($_POST['action']) || !isset($_POST['quantity'])) return;

above the line

$action = $_POST['action'];