Form Inputs updated via JS don't get submitted - php

Question

The invoice input values which hold the totals of invoice line items that get updated via JS return a NULL value when they are submitted.
<span class="sublabel">Subtotal</span><input type="text" class="total-box" id="product-subtotal" readonly="true" />
<span class="sublabel">Tax</span><input type="text" class="total-box" id="product-tax" readonly="true" />
<span class="sublabel">Total</span><input type="text" class="total-box" id="order-total" readonly="true" />
The JS
function calcProdSubTotal() {
var prodSubTotal = 0;
$(".row-total-input").each(function(){
var valString = $(this).val() || 0;
prodSubTotal += parseInt(valString);
});
$("#product-subtotal").val(prodSubTotal);
};
function calcTaxTotal() {
var taxTotal = 0;
//var taxAmount = 10;
var taxAmount = $("#salesTaxAmount").val() || 0;
var productSubtotal = $("#product-subtotal").val() || 0;
var taxTotal = parseInt(productSubtotal) * parseInt(taxAmount) / 100;
var taxTotalNice = taxTotal;
$("#product-tax").val(taxTotalNice);
};
function calcOrderTotal() {
var orderTotal = 0;
var productSubtotal = $("#product-subtotal").val() || 0;
var productTax = $("#product-tax").val() || 0;
var orderTotal = parseInt(productSubtotal) + parseInt(productTax);
var orderTotalNice = "$" + orderTotal;
$("#order-total").val(orderTotalNice);
};
$(function(){
$('.row-total-input').each(
function( intIndex ){
$('.invAmount').livequery('blur', function() {
var $this = $(this);
var amount = $this.val();
var qty = $this.parent().find('.invQty').val();
if ( (IsNumeric(amount)) && (amount != '') ) {
var rowTotal = qty * amount;
$this.css("background-color", "white").parent().find(".row-total-input").val(rowTotal);
} else {
$this.css("background-color", "#ffdcdc");
};
calcProdSubTotal();
calcTaxTotal()
calcOrderTotal();
});
}
);
});
I originally had the inputs set as disabled however I have changed them to readonly because disabled fields can't be submitted.
What am i missing?
Thanks in advance.

Answer 1

You haven't set a name-attribute on your <input />s, so PHP can't access their values, and returns nothing when you look for $_POST['product-tax']. If you have set error_reporting to E_ALL, you should see a notice telling you you are trying to access an undefined index on the $_POST array.