checkout wizard

I have successfully added "Add to Cart" buttons and everything works well with my cart page. I have opened a shipping account with UPS and a PayPal Standard account and got all the appropriate account info including an XML access key (UPS). After going through the checkout wizard, I have conducted a "checkout" run. On the cart page, I see the shipping information added. When I hit the "checkout" button, I go to checkout.php for the shipping and billing address. However, when I fill out the form and proceed to confirm.php, I get the following:

Fatal error: Call to undefined function curl_init() in C:\xampp\htdocs\guitar-tables\WA_eCart\WA_eCart_UPS_PHP.php on line 71

Here are lines 69-72:

$UPS_XML .= "</Shipment></RatingServiceSelectionRequest>";
$_SESSION[$UPS_eCart->CartName . "_UPS" . "_FullRequest"] = $UPS_XML;
if ($UPS_PkCount > 0) {
$WA_UPS_Curl = curl_init();


I do not know how to resolve this. I have tried the whole checkout wizard procedure several times with the same result.

Also, the website will be selling items of different sizes. I have added length, width and height columns to the items table, but am not sure how to dynamically pull them into the shipping info in the checkout wizard.

Thank you!