var httpRequest;
var dateFrom;
var dateTo;
var carType;
var apposition;

function calc() {
	if(window.XMLHttpRequest) httpRequest = new XMLHttpRequest();
	else if(window.ActiveXObject) {
      try {
	  	httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
	  } catch(e) {
	  	httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
	  }
	}

	httpRequest.onreadystatechange = function() {
		if(httpRequest.readyState == 4) document.getElementById('price').innerHTML = httpRequest.responseText;
 }

	dateFrom = document.getElementById('dateFrom').value;
	dateTo = document.getElementById('dateTo').value;
	carType = document.getElementById('carType').value;
	apposition = (document.getElementById('apposition')) ? document.getElementById('apposition').checked : false;
	zahranici = (document.getElementById('zahranici')) ? document.getElementById('zahranici').checked : false;

  	httpRequest.open('POST', '/calc.php', true);
	httpRequest.setRequestHeader('content-type', 'application/x-www-form-urlencoded');
	httpRequest.send('dateFrom=' + dateFrom + '&dateTo=' + dateTo + '&carType=' + carType + '&apposition=' + apposition + '&zahranici=' + zahranici);
}