[leon2009sp]

$s_model =  substr(htmlspecialchars(trim($_POST['model'])), 0, 100);
$s_marka =  substr(htmlspecialchars(trim($_POST['marka'])), 0, 100);
echo "marka====".$s_marka."<br>";
echo "model====".$s_model."<br>";

function loadXMLDoc(filename) {
        if (window.ActiveXObject) {
            xhttp = new ActiveXObject("Msxml2.XMLHTTP");
        }
        else {
            xhttp = new XMLHttpRequest();
        }
        xhttp.open("GET", filename, false);
        try { xhttp.responseType = "msxml-document" } catch (err) { } // Helping IE11
        xhttp.send(null);
        return xhttp.responseXML;
    }
    document.addEventListener('DOMContentLoaded', function () {
        var xml = loadXMLDoc("xml/db.xml"),
            selCity = document.querySelector('#marka'),
            selStation = document.querySelector('#model'),
            i;
        [].forEach.call(xml.querySelectorAll('marka'), function (el) {
            selCity.add(new Option(el.getAttribute('name'), el.getAttribute('name')))
        })
        selCity.addEventListener('change', function () {
            selStation.options.length = 0 , i=0;
            [].forEach.call(xml.querySelectorAll('marka[name=' + this.value + '] > model'), function (el) {
                selStation.add(new Option(el.textContent, ++i));
            })
        })
    })