问题
I am creating a shopping cart which has four buttons continue shopping, clear cart, update cart and place order I am facing a problem with the sessions like when I press the clear cart button it shows the
undefined index cart
but the cart comes from the session and when i press the clear cart button
it unsets the session of cart
so where i am doing it wrong ? can anyone help ? here is my code
<?php
include("includes/db.php");
include("includes/functions.php");
if($_REQUEST['command']=='delete' && $_REQUEST['pid']>0){
remove_product($_REQUEST['pid']);
}
else if($_REQUEST['command']=='clear'){
unset($_SESSION['cart']);
}
else if($_REQUEST['command']=='update'){
$max=count($_SESSION['cart']);
for($i=0;$i<$max;$i++){
$pid=$_SESSION['cart'][$i]['productid'];
$q=intval($_REQUEST['product'.$pid]);
if($q>0 && $q<=999){
$_SESSION['cart'][$i]['qty']=$q;
}
else{
$msg='Some proudcts not updated!, quantity must be a number between 1 and 999';
}
}
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Shopping Cart</title>
<script language="javascript">
function del(pid){
if(confirm('Do you really mean to delete this item')){
document.form1.pid.value=pid;
document.form1.command.value='delete';
document.form1.submit();
}
}
function clear_cart(){
if(confirm('This will empty your shopping cart, continue?')){
document.form1.command.value='clear';
document.form1.submit();
}
}
function update_cart(){
document.form1.command.value='update';
document.form1.submit();
}
</script>
</head>
<body>
<form name="form1" method="post">
<input type="hidden" name="pid" />
<input type="hidden" name="command" />
<div style="margin:0px auto; width:600px;" >
<div style="padding-bottom:10px">
<h1 align="center">Your Shopping Cart</h1>
<input type="button" value="Continue Shopping" onclick="window.location='products.php'" />
</div>
<div style="color:#F00"><?php echo'' ;?></div>
<table border="0" cellpadding="5px" cellspacing="1px" style="font-family:Verdana, Geneva, sans-serif; font-size:11px; background-color:#E1E1E1" width="100%">
<?php
if(is_array($_SESSION['cart'])){
echo '<tr bgcolor="#FFFFFF" style="font-weight:bold"><td>Serial</td><td>Name</td><td>Price</td><td>Qty</td><td>Amount</td><td>Options</td></tr>';
$max=count($_SESSION['cart']);
for($i=0;$i<$max;$i++){
$pid=$_SESSION['cart'][$i]['productid'];
$q=$_SESSION['cart'][$i]['qty'];
$pname=get_product_name($pid);
if($q==0) continue;
?>
<tr bgcolor="#FFFFFF"><td><?php echo $i+1?></td><td><?php echo $pname?></td>
<td>$ <?php echo get_price($pid)?></td>
<td><input type="text" name="product<?php echo $pid?>" value="<?php echo $q?>" maxlength="3" size="2" /></td>
<td>$ <?php echo get_price($pid)*$q?></td>
<td><a href="javascript:del(<?php echo $pid?>)">Remove</a></td></tr>
<?php
}
?>
<tr><td><b>Order Total: $<?php echo get_order_total()?></b></td><td colspan="5" align="right"><input type="button" value="Clear Cart" onclick="clear_cart()"><input type="button" value="Update Cart" onclick="update_cart()"><input type="button" value="Place Order" onclick="window.location='billing.php'"></td></tr>
<?php
}
else{
echo "<tr bgColor='#FFFFFF'><td>There are no items in your shopping cart!</td>";
}
?>
</table>
</div>
</form>
</body>
</html>
回答1:
If you haven't already started populating your cart then the element will be undefined. When dealing with array elements it's always better to add the additional test array_key_exists(). However in your case the problem is more about the way you handle your array generally.
PHP is quite forgiving, so you have to enforce your own disciplines on the way you code. One piece of very good practice which is worth getting used is to explicitly initialise your variables before you start using them.
// somewhere near the top of your code
$_SESSION['cart'] = array_key_exists('cart', $_SESSION)?$_SESSION['cart']:array();
and don't unset it in the clear test ... just set it back to an empty array.
else if($_REQUEST['command']=='clear'){
$_SESSION['cart'] = array();
}
回答2:
here is Simple PHP Shopping Cart Tutorial
$product_id = $_GET['id']; //the product id from the URL
$action = $_GET['action']; //the action from the URL
//if there is an product_id and that product_id doesn't exist display an error message
if($product_id && !productExists($product_id)) {
die("Error. Product Doesn't Exist");
}
switch($action) { //decide what to do
case "add":
$_SESSION['cart'][$product_id]++; //add one to the quantity of the product with id $product_id
break;
case "remove":
$_SESSION['cart'][$product_id]--; //remove one from the quantity of the product with id $product_id
if($_SESSION['cart'][$product_id] == 0) unset($_SESSION['cart'][$product_id]); //if the quantity is zero, remove it completely (using the 'unset' function) - otherwise is will show zero, then -1, -2 etc when the user keeps removing items.
break;
case "empty":
unset($_SESSION['cart']); //unset the whole cart, i.e. empty the cart.
break;
}
?>
from here
回答3:
switch($action) { //decide what to do
case "add":
$_SESSION['cart'][$product_id]++; //add one to the quantity of the product with id $product_id
break;
case "remove":
$_SESSION['cart'][$product_id]--; //remove one from the quantity of the product with id $product_id
if($_SESSION['cart'][$product_id] == 0) unset($_SESSION['cart'][$product_id]); //if the quantity is zero, remove it completely (using the 'unset' function) - otherwise is will show zero, then -1, -2 etc when the user keeps removing items.
break;
case "empty":
unset($_SESSION['cart']); //unset the whole cart, i.e. empty the cart.
break;
来源：https://stackoverflow.com/questions/15584300/how-to-create-an-online-shopping-cart-in-php