// Function
function show_calendar(month,year) {
        JsHttpRequest.query(
            '/js/p_backend.php', // backend
            {
                // pass a text value
                'month': month,
                'year': year
            },
            // Function is called when an answer arrives.
            function(result, errors) {
                // Write the answer.
                document.getElementById("calendar").innerHTML =
                    result["str"];
            },
            false  // do not disable caching
        );
}