Binding CustomerInfo to Checkout . . .

. . . for PayPal Standard Gateway question. Why isn't this working (used the WA Recipes360 info)?
Please help with a walk-through (static site; PHP; eCart 4.5.1) . . .

1st field to be pre-filled on the Checkout page from the corresponding field on the CustomerInfo page has the following syntax(?):
<input type="hidden" name="billFirstNameText" id="billFirstNameText" value="<?php echo((isset($_POST["billFirstNameText"]))?$_POST["billFirstNameText"]:"") ?>" />
Is this correct?

And, how does one "populate" the Shipping info from the Billing info on the CustomerInfo page using a checkbox ie: "Shipping info same as Billing?"

Thanks in advance . . .

. . . has (possibly) created a positive difference, but there's a problem with the Recipes instructions (surprize!).
In re-creating the "Checkout" page (Customer Info population & read-only Shopping Cart), the actual Checkout button has a leading red exclamation point in the Server Behaviors list. When that is double-clicked to "see why" an error message pops up stating:
"Please ensure that your selection is inside the body tag before using this object"
The Checkout button is within the form element which is inside div's which are inside the body tag . . .
What's up with that?
Uploading the "new & improved" Checkout page & testing the process live leads to a blank page when the Customer Info page "proceed to Checkout" button is pressed. Of course, that means that that (technically) there's still no info being carried from the Customer Info page automatically to the Checkout page . . .
Thanks in advance to anyone out there!

A blank page generally means your server has debugging turned off. I would suggest turning it on so that you get error descriptions and line numbers at least until you have it working.

Any number of things could be wrong and a blank page is hard to debug.

There is a javascript file we include that has the function for moving information from billing to shipping. It is simple client side javascript that moves the information from one form element to the other.

. . . preceeds the HTML (doctype, etc.) - the server in question is "live" in the FL Keys. Am trying to contact them (e-mail only).
TWF_Product_Fishshapes01.php
leads to
TWF_Artisans_Checkout.php
Is this a rude interruption to your day time-wise?

<?php
//WA eCart Include
require_once("WA_eCart/eCart1_PHP.php");
?>
<?php
$eCart1->GetContent();
?>
<?php
if (!session_id()) session_start();
if("" == "") {
$_SESSION["TaxRate"] = "billStateList";
}
?>
<?php
if (!session_id()) session_start();
if("" == "") {
$_SESSION["TaxRate"] = "".((isset($_POST["billStateList"]))?$_POST["billStateList"]:"") ."";
}
?>
<?php
//WA eCart Check Out Update
if (isset($_POST["eCart1_Checkout_1"]) || isset($_POST["eCart1_Checkout_1_x"])) {
$eCart1->UpdateCart();
$eCart1->cartAction = "CheckOutUpdate";
}
?>
<?php
//WA eCart Redirect Check Out
if (isset($_POST["eCart1_Checkout_1"]) || isset($_POST["eCart1_Checkout_1_x"])) {
$Redirect_redirStr="https://www.paypal.com/cgi-bin/webscr";
if ($Redirect_redirStr != "") {
if (isset($_SERVER['QUERY_STRING']) && $_SERVER['QUERY_STRING'] != "") {
if (strpos($Redirect_redirStr, "?") === false) {
$Redirect_redirStr .= "?".$_SERVER['QUERY_STRING'];
}
else {
$Redirect_redirStr .= "&".$_SERVER['QUERY_STRING'];
}
}

$eCart1->redirStr = $Redirect_redirStr;
}
$eCart1->cartAction = "Checkout";
}
?>
<?php
// WA eCart Redirect
if ($eCart1->redirStr != "") {
header("Location: ".$eCart1->redirStr);
}
?>

. . . per the post above:
I have eliminated the 1st session "TaxRate" seemed redundant (& less info?).
In the "Bindings" panel there exist items named:
eCart1_Checkout_1_x
eCart1_Checkout_1_y
Fiddling around with those values in the "isset" sections in the "CustomerInfo" & "Checkout" pages has allowed the blank "Checkout" page to display.
Sometimes . . .
Certain combinations cause the clicking of the "Proceed to Checkout" button (CustomerInfo pg.) to bypass the Checkout page & go directly to:
webscr (btw > correct address for PayPal Standard?)
That URL is the ReDirect string for the "Checkout" page "Checkout" button . . .
The other original problems still exist > the failure of the info collected on the "CustomerInfo" page (billing & shipping) to appear on the "Checkout" page (billing & shipping, plus read-only shopping cart) so tax can be figured into the total. Binding value (sample field from "Checkout" pg.):
<?php echo((isset($_POST["billFirstNameText"]))?$_POST["billFirstNameText"]:"") ?>
Also, the column value (Color) in the Shopping Cart section (Checkout pg.) fails to carry over from the 1st "Shopping Cart" page, and (most importantly) the "TaxRate" is not shown/calculated. The Recipe360 instructions were followed . . .
Thanks in advance . . .

. . . thanks!