/*
No retorno chama a função retorno(result)!!
*/
var http_request = false;
var result = false;
function request(url, parameters) {
  http_request = false;
  if (window.XMLHttpRequest) { // Mozilla, Safari,...
    http_request = new XMLHttpRequest();
    if (http_request.overrideMimeType) {
      // set type accordingly to anticipated content type
      //http_request.overrideMimeType('text/xml');
      http_request.overrideMimeType('text/html');
    }
  } 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('Cannot create XMLHTTP instance');
    return false;
  }
  http_request.onreadystatechange = alertContents;
  http_request.open('GET', url + parameters, true);
  http_request.send(null);
}

function alertContents() {
  if (http_request.readyState == 4) {
    if (http_request.status == 200) {
      result = http_request.responseText;
      // Ação que deve ser realizada com o resultado do get.
      retorno(result);
    } else {
      alert('There was a problem with the request.');
    }
  }
}