Fatal error: Unsupported operand types

function total_items($cart)
{
    $num_items = 0;
    
    if(is_array($cart))
    {
        foreach($cart as $id => $qty)
        {
            $num_items = $num_items + var_dump($qty);
        }
        return $num_items;
    }
}

$num_items []=$qty

 $num_items = $num_items + 1

function total_price($cart)  
{
    $total_price = 0.0;
    
    db_connect();
    
    if(is_array($cart))
    {
        foreach($cart as $id => $qty)
        {
            
            $query = "SELECT price FROM products WHERE id='$id'  ";
            $result = mysql_query($query);
            if($result)
            {
                $item_price = mysql_result($result,0,'price');
                $total_price +=  $item_price * $qty;
            }
        }
        return $total_price;
    }
}

            77    $item_price = mysql_result($result,0,'price');
            78   $total_price +=  $item_price * $qty;

$num_items = $num_items + $qty;

echo $qty; echo $num_items

$qty['название поля']

$num_items = $num_items + $qty['id'];
 
$total_price +=  $item_price * $qty['id'];

<td align="center">  <?=number_format($product['price'] * $quantity ,2); ?> руб</td>

foreach ($_SESSION['cart'] as $id => $quantity):
         $product = get_product($id);
         
         $b = get_sizes($id);