function createRequest() {
  var request = null;
  try {
    request = new XMLHttpRequest();
  } catch (trymicrosoft) {
    try {
      request = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (othermicrosoft) {
      try {
        request = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (failed) {
        request = null;
      }
    }
  }

  if (request == null) {
    alert("Error creating request object!");
  } else {
    return request;
  }
}

var request = createRequest();

function showVideo(id) {
  var url = "showvid.php?id=" +id;
  request.open("GET", url, true);
  request.onreadystatechange = updateVideo;
  request.send(null);
}

function updateVideo() {
  if (request.readyState == 4) {
    if (request.status == 200) {
      var vid = request.responseText;
      document.getElementById("vidscreen").innerHTML = vid;
    } else
      alert("Error! Request status is " + request.status);
  }
}