PHP Function in ajax url?

PHP Function in ajax url?

i'm a new JQuery user and i have 2 questions ..
this is my code:
<script type="text/javascript">
$(document).ready(function(){
$('#module').change(function(){
var module = $("select#module").val();
var dataAll = 'module=' + module ;
$.ajax({
url: "name.php",
type : "POST",
data : dataAll,
dataType :"html",
success : function(msg){
$('#result').html(msg)
}
});
});
});
</script>
so first, how can i use PHP function in url field , for example i'm using
Codeigniter and i want to put base_url function as a url .
and how can i request just an id from the page, not all the page ..
thanks a lot :)