function getIDcity(){
    var xmlHttpReq;
    if(typeof XMLHttpRequest != 'undefined')
    {
      try
      {
        xmlHttpReq = new XMLHttpRequest();
      }
      catch(e)
      {
              try {
                xmlHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
              } catch (e) {
              try {
                xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
              } catch (E) {
                xmlHttpReq = false;
              }
             }
      }
    }
    else
    {
      try {
              xmlHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
            try {
              xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (E) {
              xmlHttpReq = false;
            }
      }
    }
    xmlHttpReq.open('GET', 'getcity.php?idclub='+document.forms['gig'].elements['IDclub'][document.forms['gig'].elements['IDclub'].selectedIndex].value,false);
    xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xmlHttpReq.send(null);
    var IDcity=xmlHttpReq.responseText;
    for (i=0; i<document.forms['gig'].elements['IDcity'].options.length; i++) {
        if ( document.forms['gig'].elements['IDcity'][i].value == IDcity ) {
            document.forms['gig'].elements['IDcity'].selectedIndex = i;
        }
    }
}