PHP Variables?

Newbie here with a question, My web host is running PHP 4.2.3 and I am running PHP 4.3.0 locally. Whenever I try to test a page that accepts variables (either from a form or by attaching them to the URL when calling the .php page) I get errors saying that the variables are 'undefined'. However, if I upload the same code to my web host it works fine. Did something change in 4.3.0? Am I missing something? I'd like to be able to code and test the pages locally without having to upload them everytime I want to test them. I am running PHP against IIS 5 on WinXP, the web host is using Apache. The code is listed below. Thanks for any help. <html> <head> <title>Conditionals</title> <link href="./style/styles.css" type="text/css" rel="stylesheet"> </head> <body> <table bgcolor="#9999cc" width="100%" height="100"> <tr> <td><a href="http://www.php.net/"><img src="images/php_logo.gif" border="0"/></a></td> </tr> </table> <?php /* $Quantity must be passed to this page from a form or via the URL. $Discount is optional */ $Cost = 2000.00; $Tax = 0.06; if (isset($Quantity)){ print ("No value passed");} if ($Quantity) { $Quantity = abs($Quantity); $Discount = abs($Discount); $Tax++; // Tax is now worth 1.06 $TotalCost = (($Cost * $Quantity) - $Discount) * $Tax; $Payments = round($TotalCost, 2) / 12; // Print the results print ("You requested to purchase $Quantity widget(s) at \$$Cost each.\n<p>"); print ("The total with tax, minus your \$$Discount, comes to $"); printf("%01.2f", $TotalCost); print (".\n<p>You may purchase the widget(s) in 12 monthly installments of $"); printf("%01.2f", $Payments); print (" each.\n<p>"); } ?> </body> </html>