To Save the Jquery sortable data in database

<ul id="sortable" >
<li id="id1">elem 1 </li >
<li id="id2">elem 2 </li >
<li id="id3">elem 3 </li >
<li id="id4">elem 4 </li >
</ul >

$(document).ready(function(){
$('#sortable').sortable({
update: function(event, ui) {
var sortData= $(this).sortable('toArray').toString();
$.get('ajaxfilename.php', {order:sortData});
}
});
});

here sortData will get changed whenever a change is made in the Sortable