// Функция вызывается при нажатии на кнопку.
function getDistrict(form) {
    var st={};
    st['town']=form.town.value;
    st['lang']=form.lang.value;
    // Create new JsHttpRequest object.
    var req = new JsHttpRequest();
    // Enable caching of the query results
    req.caching = false;
    // Code automatically called on load finishing.
    req.onreadystatechange = function() {
        if (req.readyState == 4) {
            // Write result to page element (_RESULT becomes responseJS).
            document.getElementById('district').innerHTML = req.responseJS.district ;
        }
    }
    // Prepare request object (automatically choose GET or POST).
    req.open('get', '/get_district.php', true);
    // Send data to backend.
    req.send( st );
    return false;
}