Shopping cart issues

[Rap_Jones]

Please bear with me, I've only been using PHP for a couple of months and mostly for light fill in the blank variable kind of pages. This is me stepping up the challenge a bit and trying new things.

I'm writing a shopping cart. For a while it worked fine, but I noticed that if a user clicked on an item twice, rather than updated the quantity field in the database, it would add an entirely new entry. So what I want to do here is check first to see if this user has already added the item. If they have, update only the quantity field and if not, then add a new entry. As you may have suspected, this doesn't work for me and I'm sure it's my inexperience biting me in the ***. All help is greatly appreciated.

<?php

session_start();
header("Cache-control:private");

include("dblogin.php");
include("showerror.php");

$itemToAdd = $_GET['movieID'];
$custID = $_SESSION['custID'];

$sql1 = "SELECT * FROM cart WHERE cartCustID = '$custID'";
$query1 = mysql_query($sql1) or die (showerror());

while($row1 = mysql_fetch_array($query1)) {

	if($row1[cartItemID] = $itemToAdd) {

		$sql2 = "UPDATE cart SET qty = qty + 1";
		$query2 = mysql_query($sql2) or die (showerror());
		mysql_select_db($dbname, $connection);

		if($query2) {

			header("Location:cart.php");

		} else {

			echo("<h3>There's something wrong!,/h3>");
			showerror();

		}

	} else {

		$sql3 = "INSERT INTO cart (cartID, cartCustID, CartItemID, qty) VALUES (0, $custID, $itemToAdd, 1)";
		$query3 = mysql_query($sql3) or die (showerror());
		mysql_select_db($dbname, $connection);

			if($query3) {

				header("Location:cart.php");

			} else {

				echo("<h3>There's something wrong!</h3>");
				showerror();

			}

		}

	}


?>

A couple of notes. The variables $dbname and $connection are both referenced from the included file dblogin.php. The function showerror() is referenced in the included file showerror.php. Both of these are working fine.

[bongbong]

in line:

if($row1[cartItemID] = $itemToAdd)

should it be "==" for comparison?

[yahyac]

Yes.

[Rap_Jones]

I've found a bunch of errors in the code and have resolved them.

The updated code:

<?php

session_start();
header("Cache-control:private");
error_reporting(E_ALL);

include("dblogin.php");
include("showerror.php");

$custID = $_SESSION['custID'];

/* $sql = "INSERT INTO cart (cartID, cartCustID, cartItemID, qty, cost) VALUES (0, '$custID', '$itemToAdd', 1, '$cost')";
$query = mysql_query($sql);

if($query) {

	header("Location:cart.php");

} else {

	echo("<h3>There's something wrong.</h3>");
	showerror();

} */

$sql1 = "SELECT * FROM cart WHERE cartCustID = '$custID'";
$query1 = mysql_query($sql1);

 while($row1 = mysql_fetch_array($query1)) {

 		if($row1['cartItemID'] == $itemToAdd) {

			$itemToAdd = $_GET['movieID'];
			$cost = $_GET['cost'];		
			$sql2 = "UPDATE cart SET qty = qty + 1";
			$query2 = mysql_query($sql2);
			mysql_select_db($dbname, $connection);

		if($query2) {

			header("Location:cart.php");

		} else {

			echo("<h3>There's something wrong!,</h3>");
			showerror();

		}

	} else {

		$sql3 = "INSERT INTO cart (cartID, cartCustID, CartItemID, qty, cost) VALUES (0, '$custID', '$itemToAdd', 1, '$cost')";
		$query3 = mysql_query($sql3);
		mysql_select_db($dbname, $connection);

			if($query3) {

				header("Location:cart.php");

			} else {

				echo("<h3>There's something wrong!</h3>");
				showerror();

			}

		}

	} 


?>

It seems to trip up on:

while($row1 = mysql_fetch_array($query1)) {

Don't know why. That just seems to be where the script stops working. The commented out script above the main script is a working, much simpler version, but it doesn't do what I need it to do.