function sendMessage(form) {
  document.getElementById("form-sending").innerHTML = "Sending";

  xmlhttp = getXmlHttpObject();
  
  // If you don't have AJAX, output this message and stop.
  if (xmlhttp == null) {
    alert("Your browser does not support AJAX!");
    return;
  }
  
  var requestURL = "signUp.php?name=" + form.name.value + "&email=" + form.email.value + "&message=" + form.message.value;
  
  // Set up event listener
  xmlhttp.onreadystatechange = stateChanged;
  // Send request
  xmlhttp.open("GET", requestURL, true);
  xmlhttp.send(null);
}

function stateChanged() {
  if (xmlhttp.readyState == 4) {
    document.getElementById("form-sending").innerHTML = "";
    document.getElementById("form-name").value = "";
    document.getElementById("form-email").value = "";
    document.getElementById("form-message").value = "";
    
    alert(xmlhttp.responseText);
  }
}

function getXmlHttpObject() {
  if (window.XMLHttpRequest) {
    // IE7+, Firefox, Chrome, Opera, Safari
    return new XMLHttpRequest();
  }
  if (window.ActiveXObject) {
    // IE6, IE5
    return new ActiveXObject("Microsoft.XMLHTTP");
  }
  return null;
}