need some help calculating

[jwk811]

i have a cart on my site and i have to figure out the total weight of the order using the weight and quantity..  so i get the weight and qty from the db which is in their cart and i need to multiply each weight and qty together and sum up all the products total weight.. understand? i think im going to need to use a for or while but im not sure and i dont really know how to do that.. thanks for any help!

[mattd8752]

I think $weight1 = $item1*amount
$weight2 = $item2*amount
...  do this for every item then
$tweight = $weight1 + $weight2; ect.  You would then end up with the total weight, then just use your shopping cart script to find the price of the items.  If you used this way it would be simpler than looping.  In terms of optimization looping might be faster.  You will have to ask someone more experienced about that.

[GingerRobot]

I think we're really going to need some information on your database structure to help you

[jwk811]

ok my table it set up like this for the cart:
product_id/qty/session_id
then i find the weight of the product_id from another table- product:
product_id/weight/price
in the cart i need to multiply the qty by the weight for each product.. understand?

- and matt that would take too long and might not work out right.. hopin theres somethin easy to do this.. thanks!

[GingerRobot]

Something like this should work:

[code]
<?php
$sql = "SELECT * FROM `cart` WHERE `session_id`='$sessionid'";
$result = mysql_query($sql) or die(mysql_error());
$total_weight = 0;
while($row=mysql_fetch_assoc($result)){
$product_id = $row['product_id'];
$qty = $row['qty'];
$sql = "SELECT `weight` FROM `products` WHERE `product_id`='$product_id'";
$weight_result = mysql_query($sql) or die(mysql_error());
$weight = mysql_result($weight_result,0,"weight");
$item_weight = $weight * $qty;
$total_weight = $total_weight+$item_weight;
}
echo "Total weight: $total_weight";
?>
[/code]

Obviously you're gonna have to modify it a bit to work with your database and variables. Its also untested.

[jwk811]

this came up.. mysql_result(): weight not found in MySQL result index 23 ..  anyone know what the problem is?

[jwk811]

NEVERMIND GOT IT! THANKS GINGER!

[Barand]

or single query

[code]
<?php
$sql = "SELECT SUM(c.qty * p.weight)
        FROM cart c INNER JOIN product p ON c.product_id = p.product_id
        WHERE c.session_id = '$sessid' ";
$res = mysql_query($sql) or die (mysql_error());
$total_weight = mysql_result($res, 0);
?>
[/code]