var ajax_target='';
var ajax_old_param=false;
var ajax_global_param=false;
var ajax_active=false;
var ajax_responseHandler;

function check_for_change() {
  if (!ajax_old_param || ajax_global_param!=ajax_old_param) {
    ajax_old_param=ajax_global_param;
  } else {
    window.clearInterval(ajax_active);  
    ajax_active=false;
    ajax_call(ajax_global_param);
  }
}

function ajax_call (param) {
  if (typeof ajax_target=='undefined') {
    responseHandlerName=ajax_target;
  } else {
    responseHandlerName=ajax_responseHandler.name;
  }
  try {
    xmlhttp=window.XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP"); 
  } catch(e) {
    // kein AJAX in diesem Browser unterstützt
  }
  xmlhttp.onreadystatechange=ajax_responseHandler;
  xmlhttp.open("GET","?ajax="+responseHandlerName+"&"+param);
  xmlhttp.send(null); // bei POST-Requests hier den Querystring rein
}

function ajax (formular,responseHandler,target,gap) {
  if (typeof target!='undefined') { ajax_target=target; }
  var param='';
  if (formular.elements) {
    for (var i=0;i<formular.elements.length;i++) {
      if (formular.elements[i].type=='select-one') {
        param=param+formular.elements[i].name+'='+formular.elements[i].value+'&';
      }
      if (formular.elements[i].type=='text') {
        param=param+formular.elements[i].name+'='+formular.elements[i].value+'&';
      }
      if (formular.elements[i].type=='hidden') {
        param=param+formular.elements[i].name+'='+formular.elements[i].value+'&';
      }
      if (formular.elements[i].type=='radio' && formular.elements[i].checked) {
        param=param+formular.elements[i].name+'='+formular.elements[i].value+'&';
      }
      if (formular.elements[i].type=='checkbox' && formular.elements[i].checked) {
        param=param+formular.elements[i].name+'='+formular.elements[i].value+'&';
      }
    }
    param=param.substr(0,param.length-1);
  } else {
    param=formular.replace(/(.*)\?/,'');
  }
  ajax_global_param=param;
  ajax_responseHandler=responseHandler;
  if (typeof gap!='undefined') { 
    if (!ajax_active) { ajax_active=window.setInterval("check_for_change()",gap); }
  } else {
    ajax_call(param); 
  } 
}