function summa(data_za,data_od,nomer,oplata,valuta) {
    // Create new JsHttpRequest object.
    var req = new JsHttpRequest();
    // Code automatically called on load finishing.
    req.onreadystatechange = function() {
        if (req.readyState == 4) {
		  var response = req.responseText;
    	  myDiv = document.getElementById("suma2");
    	  myDiv.innerHTML = response;
        }
    }
    // Prepare request object (automatically choose GET or POST).
    req.open(null, 'summa.php', true);
    // Send data to backend.
    req.send( { data_za: data_za, data_od: data_od , nomer: nomer , oplata: oplata , valuta: valuta } );
}