Question

I have a problem with my code:

<?php 
    echo $s_country;
    $sql2="SELECT prod_id FROM tbl_order_item WHERE order_id='$order_id'";
    $res=mysql_query($sql2) or die(mysql_error());
    $i=0;
    $j="";
    while($rs=mysql_fetch_array($res)){
        $j = $rs['prod_id']; 
        if(trim($s_country)=='US' || trim($s_country=='United States' )){
            $sql3 = "SELECT shipping_us FROM tbl_product WHERE prod_id=".$j;
            $res=mysql_query($sql3) or die(mysql_error());
            $shipping_cost1=mysql_fetch_object($res);  
        }
        $i++;
    }
?>

What I actually want to do is to fetch the products id from the table tbl_order_item and with that products id select the shipping cost for those ids from the table tbl_product.

For example, if there is two product ids, it should select shipping cost for both the ids.
But here it only works for one product id like this:

SELECT shipping_us FROM tbl_product WHERE prod_id=526

But what I’m trying to do is :

SELECT shipping_us FROM tbl_product WHERE prod_id=526
SELECT shipping_us FROM tbl_product WHERE prod_id=527

Answer 1

First Solution:

Change

$res=mysql_query($sql3) or die(mysql_error()); // you have overwritten result set of first query
$shipping_cost1=mysql_fetch_object($res);  

To

$newres=mysql_query($sql3) or die(mysql_error());
$shipping_cost1=mysql_fetch_object($newres);

Second Solution (much better):

$sql2="SELECT GROUP_CONCAT(prod_id SEPARATOR ',') as pid FROM tbl_order_item WHERE order_id='$order_id'";
$res=mysql_query($sql2) or die(mysql_error());

if(mysql_num_rows($res) > 0){
  $rs=mysql_fetch_array($res);
  $sql3 = "SELECT shipping_us FROM tbl_product WHERE prod_id IN (".$rs['pid'].")";
  $res=mysql_query($sql3) or die(mysql_error());
  while ($row = mysql_fetch_array($res)){
     echo $row['shipping_us']
  }
}

Recommendations:

1.Learn to prevent from MySQL Injections: Good Link

2.Mysql extension is not recommended for writing new code. Instead, either the mysqli or PDO_MySQL extension should be used. More reading: PHP Manual