function add_prod_to_cart(id) {
    // Create new JsHttpRequest object.
   // alert(value);
    var req = new JsHttpRequest();
    // Code automatically called on load finishing.
    req.onreadystatechange = function() {
        if (req.readyState == 4) {
            // Write result to page element (_RESULT becomes responseJS). 
            
            createMessage( req.responseJS.m, 'white', 5000 );
            //alert(req.responseJS.m);
            document.getElementById('Quantity').innerHTML =  req.responseJS.quantity;
            document.getElementById('Total_cost').innerHTML =  req.responseJS.cost;
                        
            // Write debug information too (output becomes responseText).
            //document.getElementById('debug').innerHTML = req.responseText;
            
        }
    }
    // Prepare request object (automatically choose GET or POST).
    req.open(null, '../lib/add_to_backet.php', true);
    // Send data to backend.
    req.send( { good_id: id } );
}