var http_request = false;

function makeRequest(url) {
http_request = false;

if (window.XMLHttpRequest) { // Mozilla, Safari,...
http_request = new XMLHttpRequest();
if (http_request.overrideMimeType) {
http_request.overrideMimeType('text/xml');
}
} else if (window.ActiveXObject) { // IE
try {
http_request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
http_request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {}
}
}

if (!http_request) {
alert('Giving up :( Cannot create an XMLHTTP instance');
return false;
}

http_request.onreadystatechange = alertContents;
http_request.open('POST', url, true);
var period = document.getElementById('period').value;
http_request.send(period);
}

function alertContents() {
if (http_request.readyState == 4) { // COMPLETED
if (http_request.status == 200) { // HTTP STATUS 
document.getElementById('result').innerHTML=http_request.responseText;
//alert(http_request.responseText);
} else {
alert('There was a problem with the request.');
}
}
}

function setPresent(VALUE) {
var present = '';
arr = VALUE.split('-');
period = arr[0];
switch (period) {
case '1': present = '—'; break;
case '3': present = '+ 3 месяца'; break;
case '6': present = '+ 6 месяцев'; break;
case '9': present = '+ 9 месяцев'; break;
case '12': present = '+ 1 год!'; break;
}document.getElementById('present').innerHTML = present;
}