var xmlHttp = getXmlHttpObject();

function populateSubSelection(select1,select2,val){

//Recupero i dati da inviare 
var mainSelection = document.getElementById(select1); 
var selezionato=mainSelection.options[mainSelection.selectedIndex].value;
//Recupero la seconda SELECT 
subSelection = document.getElementById(select2); 
//Svuoto la secondo SELECT 
for (var i = subSelection.length - 1; i >= 0; i--) 
subSelection.remove(i); 

xmlHttp.open('GET', 'comune_ajax.php?choice=' + selezionato + '&op=' + val, true);
xmlHttp.onreadystatechange = stateChanged;
xmlHttp.send(null);
}



function stateChanged() {


	if(xmlHttp.readyState == 4) {
		//Stato OK
		if (xmlHttp.status == 200) {
			var resp = xmlHttp.responseText;
			
			if(resp) {
				
				resp=resp.replace(/\s+$|^\s+/g,"");
				
				//Le coppie di valori nella stringa di risposta sono separate da ;
				var values = resp.split(';');
								
				var select = subSelection;
				
				//Elimina i valori precedenti
				while (select.options.length) {
					select.remove(0);
				} 
				
				var limit = values.length-1;
				
				var option = document.createElement("option");
					option.value = '',
					option.text = 'Seleziona';
					try {
							select.add(option, null);
						} catch(e) {
							//Per Internet Explorer
							select.add(option);
						}	
				
				for(i=0; i < limit; i=i+2) {
					
					//aggiunge un elemento <option>
					var option = document.createElement("option");
					option.value = values[i],
					option.text = values[i+1];
					try {
							select.add(option, null);
						} catch(e) {
							//Per Internet Explorer
							select.add(option);
						}	
					
				}
			}
		} else {
			alert(xmlHttp.responseText);
		}
	}	
}


function getXmlHttpObject()
{
  var xmlHttp=null;
  try
    {
    // Firefox, Opera 8.0+, Safari
    xmlHttp=new XMLHttpRequest();
    }
  catch (e)
    {
    // Internet Explorer
    try
      {
      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
    catch (e)
      {
      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    }
  return xmlHttp;
}




function azzera(val)
{
var subSelection=document.getElementById(val)
for (var i = subSelection.length - 1; i >= 0; i--) 
subSelection.remove(i); 

var NewOpt = document.createElement('option'); 
	NewOpt.value = ""; 
	NewOpt.text = "-"; 
	try{ 
	subSelection.add(NewOpt, null); //Metodo Standard, non funziona con IE 
	}catch(e){ 
	subSelection.add(NewOpt); // Funziona solo con IE 
	} 
}