shopping cart problem (newbie)

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August 10th, 2003, 11:57 PM

bmy78

Junior Member

Join Date: Feb 2003

Posts: 6

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shopping cart problem (newbie)

Hi all,

I've been having a problem building a basic shopping cart, which is modelled after the "persistent shopping cart" tutorial. It works fine, however, every time I hit the "refresh" button on my Web browser, it adds an additional item to the cart (but only when the quantity is set to 1, if I set it higher it won't add it). The code is below. Can anyone tell me what I'm doing wrong, I'm not sure what I'm seeing.

The cart.php code

PHP Code:


		
			
[SIZE=1]

<?php

session_start();



// set cookie

setcookie("cart_id", session_id(), time() + ((3600 * 24) * 30));



?>



<html>

<head>

<title>Buy My Junk.com</title>

<script language="JavaScript">

        function UpdateQty(item)

        {

            item_id = item.name;

            newQty = item.options[item.selectedIndex].text;

            document.location.href='cart.php?action=update_ite  m&id='+item_id+'&qty='+newQty;

        }

</script>    

</head>



<body>

<table border="1" width="100%" cellspacing="0" cellpadding="0">

<tr>

    <!-- HEADER FOR LOGO, 468x60 BANNERS ----------------->

    <td colspan="2">

    <h1>Buy My Junk.com</h1>

    </td>

    </tr>

    <tr>

    <td width="85%" align="right">

    LINK | LINK | LINK | LINK | LINK

    &nbsp;

    </td>

    <td align="right">

    <input type="text" size="10" value="Search">&nbsp;<input type="button" value="Go!"></td>

    </tr>

<tr>

    <td width="15%" colspan="3" width="70%" valign="top">

    <h2>View Cart</h2>

    

    

        

            <?php

            

                // includes

                require("./data/functions.php");

                

                // connect to db

                db_connect();

                

                switch($_GET["action"])

                {

                    case "add_item":

                    {

                        AddItem($_GET["id"], $_GET["qty"]);

                        ShowCart();

                        break;

                    }

                    case "update_item":

                    {

                        UpdateItem($_GET["id"], $_GET["qty"]);

                        ShowCart();

                        break;

                    }

                    case "remove_item":

                    {

                        RemoveItem($_GET["id"]);

                        ShowCart();

                        break;

                    }

                    default:

                    {

                        ShowCart();

                    }

                }

                

                

                

                

            ?>

            

        

    

</td>

</tr>    

<td colspan="3">&nbsp;</td>

</tr>

</table>









</td></tr>

</table>









</body>

</html>[/SIZE]

and here's the ShowCart() function in the include file functions.php

PHP Code:


		
			
function ShowCart()

{

    $result = mysql_query("select * from cart inner join products on cart.item_id = products.item_id where cart.cookie_id = '" . GetCartId() . "' order by products.item_name asc")

        or mysql_error($result);

    

    // once we've retrieved the list, each item is displayed as part of a table, as a table row

    echo "<table border='1' cellspacing='0' cellpadding='2' class='cart'>";

    

    $color1 = "gray";

    $color2 = "lightgray";

    $row_count = 0;    

    while($row = mysql_fetch_array($result))

    {

        // increment the total cost of all items

        $totalCost += ($row["qty"] * $row["item_price"]);

    

        // alternating table colors

        $row_color = ($row_count % 2) ? $color1: $color2;

        ?>

         <tr><td bgcolor="<?php echo $row_color;?>">

         <font face='verdana' size='1' color='black'>

         <select name='<?php echo $row['item_id'];?>' onChange='UpdateQty(this)'

                 

        <?php

        for ($i = 1; $i <= 20; $i++)

        {

            echo "<option ";

            if ($row["qty"] == $i)

            {

                echo " SELECTED ";

            }

            

            echo ">" . $i . "</option>";

        }

        ?>

        </select></font></td>

        <td width="60%" height="25" bgcolor="<?php echo $row_color;?>">

        <font style="color:#FFFFFF;font-size:12pt;font-weight:bold;" face="verdana,arial,helvetica,sans-serif" size='1' color='black'>

         <?php echo $row["item_name"];?> </font></td>

        <td width="20%" height="25" bgcolor="<?php echo $row_color;?>">

        <font style="font-size:12pt;font-weight:bold;" face='verdana' size='1' color='white'>$  

        <?php echo number_format($row['item_price'], 2, '.', ',');?></font>        </td>

<td width="10%" height="25" bgcolor="<?php echo $row_color;?>">

        <font face='verdana' size='1' color='black'>

        <a href=cart.php?action=remove_item&id=<?php echo $row['item_id'];?>>Remove</a>

        </font></td>        </tr>

    <?php

    

    // increase row count by 1

    $row_count++;

    

    }

    ?>

    

    <tr><td width='100%' colspan='4'>

    <hr size='1' color='red' NOSHADE>

    </td></tr>

    <tr><td width='70%' colspan='2'>

    <font face='verdana' size='1' color='black'>

    <a href='products.php'><< Keep Shopping</a>

    </font></td>    

    <td width='30%' colspan='2'>

    <font face='verdana' size='2' color='black'>

    <b>Total: <?php echo number_format($totalCost, 2, ".", ",");?> </b>

    </font></td></tr>

    <tr><td align="right" colspan="4">

    <a href="checkout.php">Checkout >></a>

    </td></tr>

    </table>

<?php    

}

August 16th, 2003, 02:01 PM

pentapenguin

Contributing User

Join Date: Dec 2002

Posts: 51

Time spent in forums: 36 m 7 sec
Reputation Power: 6

Whenever you click on a link, the browser sends a request to the server.
If you hit refresh, the browser sends a new request to the server.
So the shopping cart gets 2 commands to add the product.
That's why new stuff is added.
I didn't read all of your code, so just say if I missed something.

August 18th, 2003, 01:22 AM

jpipes

Junior Member

Join Date: Aug 2003

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The problem is most likely in the AddItem method. Please post the code for that method so we can see what the issue is.

August 18th, 2003, 10:26 PM

bmy78

Junior Member

Join Date: Feb 2003

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Okay, here's the AddItem() function, along with UpdateItem():

PHP Code:


		
			
[small]

// The AddItem function is used to add items to your shopping cart. 

// It also checks to see if this item already exists in your shopping cart.



function AddItem($item_id, $qty)

{

    

    // MySQL query    

    $result = mysql_query("SELECT count(*) from cart WHERE cookie_id='" . GetCartId() . "' and item_id = $item_id");

    

    // set numRows variable to first row in array

    $numRows = $row[0];

    

    // if numRows value equals 0

    // we will add the item into the cart table

    

    if ($numRows == 0)

    {

        // This item doesn't exist in the users cart.

        // We will add it with an insert query

        

        @ mysql_query("Insert into cart(cookie_id, item_id, qty) values('" . GetCartId() . "', $item_id, $qty)");

    }

    else

    {

        // This item already exists in the users cart

        // We will update it instead.

        

        UpdateItem($item_id, $qty);

    }

}





// Used to update an item in the cart table.

// simple UPDATE MySQL query on the cart table

// The cookie_id field is used to match the session_id to that product

// so that the quantity is only updated for that one user and product.



function UpdateItem($item_id, $qty)

{

    mysql_query("update cart set qty=$qty where cookie_id = '" . GetCartId() . "' and item_id = $item_id");

}[/small]

August 18th, 2003, 10:31 PM

jpipes

Junior Member

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If you take off the error suppression (the @ sign in front of your mysql_query call), does the page return an error when the qty is greater than 1?

August 18th, 2003, 10:50 PM

bmy78

Junior Member

Join Date: Feb 2003

Posts: 6

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No, I don't get any errors when I remove the @, but if I add another item in the cart when there's already a quantity, it doesn't up the quantity, it just adds that item on a different line. I can have a qty of 3 on the 1st line and a qty of 1 on the 2nd.

August 18th, 2003, 10:58 PM

jpipes

Junior Member

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Does the cart table have a primary key on cookie_id and item_id? If it does, I don't see how you can insert 2 lines into the table with the same cookie_id and item_id, but different quantities...

Check the table to see that the primary key exists...

Also, your update_item function is not incrementing the qty by the qty passed to it, but simply replacing the quantity that's in the table already. Is that the desired functionality? If not, change the SQL to read UPDATE cart SET qty=qty + $qty WHERE cookie_id = " . GetCartID() . " and item_id = $item_id

HTH

January 26th, 2004, 07:59 AM

aloo

Registered User

Join Date: Jan 2004

Posts: 26

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hi

i also had the same problem.
what you have sugessted has fixed it a bit.
what happens when i add item from product.php, it increases the quantity. but when i try to change the quantity from cart.php using the combo box, this doesnt work.

thanks

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