数据不存储在数据库中

Question

我正在开发一个电子商务网站。其中，我添加了购物车的代码。但是，它无法将数据存储在mysql的cart表中。

以下是代码：

  $host = "localhost";
  $user = "root";
  $password = "";
  $database = "puri_database";

  $db = mysqli_connect($host, $user, $password, $database);

  //Function for getting user ip address
  function getRealIpAddr() {
       if (!empty($_SERVER['HTTP_CLIENT_IP']))
       //check ip from share internet
       {
       $ip=$_SERVER['HTTP_CLIENT_IP'];
       }
       elseif (!empty ($_SERVER['HTTP_X_FORWARDED_FOR'])) {
       $ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
       }
       else{
       $ip=$_SERVER['REMOTE_ADDR'];
       }
       return $ip;
  }

   function cart() {

           global $db;
           if(isset($_GET['add_cart'])){             

           $p_id = $_GET['add_cart'];
           $ip_add = getRealIpAddr();

           $check_pro = "select * from cart where p_id='$p_id' AND ip_add='$ip_add'";
           $run_check = mysqli_query($db,$check_pro);

           if(mysqli_num_rows($run_check)>0){
            echo "Product is Already Exist";
           }
           else{
            $q = "insert into cart (p_id,ip_add) values ('$p_id','$ip_add')";
            $run_q = mysqli_query($db,$q);
            echo "Product is added to cart successfully";
           }

           }
   }

你能帮我们解决这个问题吗？