var httpObject = createXMLHttpRequest();

function bestemming(thisSelected) {
    var selected = document.getElementById('flight_from');
    httpObject.onreadystatechange = bestemming_response;
    httpObject.open('GET', '/scripts/ticket_http_object.php?fill=1&selected=' + thisSelected + '&code=' + selected.options[selected.selectedIndex].value);
    httpObject.send(null);
}

function bestemming_response() {
    if (httpObject.readyState == 4) {
        var response = httpObject.responseText;
        document.getElementById('field_flight_to').innerHTML = response;
    }
}

// Creates new XMLHttpRequest
function createXMLHttpRequest() {
    var xmlHttp;
    try {
        // create an XMLHttpRequest object
        xmlHttp = new XMLHttpRequest();
    } catch(e) {
        // assume IE6 or older
        try {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")
        } catch(e) {
            alert("Error creating the XMLHttpRequest object.");
        }
    }
    return xmlHttp;
}