Update my content into XML-file

I just gratefully managed to load the content of an XML-file into my php-document, like so:

$(document).ready(function () { 
    $.ajax({ 
        type: "GET", 
        url: "abstimmer.xml", 
        dataType: "xml", 
        success: function (xml) { 
            var $lis = $(".abstimmer li");
            $(xml).find('klick').each(function (index) {
                if (index < $lis.length) {
                    $lis.eq(index).html($(this).text());
                }
            });
        }
    })
})

By that, the content of these nodes get pushed into the li-elements of the parental ul-element identifiable with class "abstimmer".

I now want to also push data from the php-file back into the xml-file. I'd like to do this by counting the clicks on a li-element, what I do in that manner:

$(".abstimmer li").click(function(){
    this.clicked=this.clicked?this.clicked+1:1;
$(this).html(this.clicked)
var klick_neu = $(this).html(this.clicked);
// Where would I need to go from here?
});

I know, that I now need to send var klick_neu to a php-file that somehow parses the var klick_neu and pushes it into that xml-file. But I have no clue how to do that. Could somebody help me with that?

And I am not sure, if that's alright with stackoverflows' rules, but I am just curious on an additional thing within the same problem: If I just added an onClick-Event within the ready-function, I could "seamlessly" load the updated content of the xml-file into my list - right?

Thanks a lot.