Store Different Value In The Database From The Forms Created Dynamically Using PHP?

Have a look at the screenshot below. As per the screenshot, I have the data fetched into the different blocks based on the database. For example, based on the username and passwo

Solution 1:

To expand on what @Logan Wayne pointed out...

An ID should be unique within a page. However, if more than one element with the specified ID exists, the getElementById() method returns the first element in the source code.

So, in your JavaScript, when you grab references to your table data elements, you'll always get the FIRST instance of a Document object with whatever id you provide.

// 2. Define what to do when XHR feed you the response from the server - Start

var product = document.getElementById("product").value; <-- will always return the same element 
var pp1 = document.getElementById("pp1").value; <-- will always return the same element
var rp1 = document.getElementById("rp1").value; <-- will always return the same element 
var stacking = document.getElementById("stacking").value; <-- will always return the same element 

You'll either have to assign unique ids to your td objects, or, again as @Logan Wayne mentioned, utilize the class property of HTML DOM objects.

Classes can be used to group like elements. After assigning class names to the different columns in your table (Product, Promotional Price, Regular Price, Stacking) you can use getElementsByClassName() to get an array of the td elements.

...
var products = document.getElementsByClassName("product"); <-- array of product td elements
...