I have a form that looks like this:
You have to send Labels within hidden inputs, etc:
<form method="post" id="aodform">
<label for="a">Animal:</label>
<input type="hidden" name="a_label" value="Animal"/>
<input class="input" type="text" name="a"/>
<label for="s">Sausage:</label>
<input type="hidden" name="s_label" value="sausage"/>
<input class="input" type="text" name="s"/>
<label for="g">Bird:</label>
<input type="hidden" name="g_label" value="bird"/>
<input class="input" type="text" name="g"/>
<label for="d">Dessert:</label>
<input type="hidden" name="d_label" value="dessert"/>
<input class="input" type="text" name="d"/>
<input id="submitter" type="submit"/>
</form>
and then in PHP you access pairs:
$name = "a"; // "s", "g", "d"
$tag = $_POST[$name.'_label'];
$value = $_POST[$name];
$xml_element = "<$tag>$value</$tag>";
OR
use same name as label and then use:
foreach($_POST as $key => $value)
{
$xml_element = "<$key>$value</$key>";
...
}
You won't be able to create or edit a local XML file using javascript/jquery because of security concerns. Imagine going to a website and the webmaster wrote some code doing who knows what and puts this in a file on your computer...
The only way to write to a local file using javascript is to use cookies or HTML5 localStorage.
localStorage will allow you to store string keys and values of arrays and/or property names and values of objects.
If you need an XML file you will have to call a server-side script that has permission to write the file on the server, which you can then access via it's url.
jQuery and Javascript on the client-side cannot persist to the server side. It has no access to write to code. You will have to gain access to a server-side language, or make use of some cloud-based services (you could, for example, persist to Amazon 3S, or a MongoDB or something of that nature, through Javascript API calls, on a cloud service).
While you could use Javascript/jQuery to construct an XML object in the client, you would then have to submit that to some server-side script to save it to a file.
Sorry to be the bearer of bad news, but you will need to get into something a bit more full-featured, if you want to be able to get this done.