function requestStates() {
    var sId = document.getElementById("country_id").value;
    var oXmlHttp = zXmlHttp.createRequest();
    oXmlHttp.open("get", "get_states_by_country.php?id=" + sId, true);
    oXmlHttp.onreadystatechange = function() {
    if (oXmlHttp.readyState == 4) {
        if (oXmlHttp.status == 200) {
            displayStates(oXmlHttp.responseText);
        } else {
            displayStates("An error occured: " + oXmlHttp.statusText);
        }
    }
    }
    oXmlHttp.send(null);
}

function displayStates(sText) {
    var divStates = document.getElementById("divStates");
    divStates.innerHTML = sText;
    requestCities();
}



function requestCities() {
    var sId = document.getElementById("state_id").value;
    var oXmlHttp = zXmlHttp.createRequest();
    oXmlHttp.open("get", "get_cities_by_state.php?id=" + sId, true);
    oXmlHttp.onreadystatechange = function() {
    if (oXmlHttp.readyState == 4) {
        if (oXmlHttp.status == 200) {
            displayCities(oXmlHttp.responseText);
        } else {
            displayCities("An error occured: " + oXmlHttp.statusText);
        }
    }
    }
    oXmlHttp.send(null);
}

function displayCities(sText) {
    var divCities = document.getElementById("divCities");
    divCities.innerHTML = sText;
}