I used a bit of javascript and a separate internal web page written in PHP. That's it. In this case, I didn't even use any XML.
Javascript
var req;
function initPage() {
kaTimer=setInterval(keepAlive, 1000);
}
function keepAlive() {
var url = "/mt/keepalive.php?aid=<TMPL_VAR _
NAME=AUTHOR_ID>&eid=<TMPL_VAR NAME=ID>";
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
req.onreadystatechange = processReqChange;
req.open("GET", url, true);
req.send(null);
} else if (window.ActiveXObject) {
req = new ActiveXObject("Microsoft.XMLHTTP");
if(req){
req.onreadystatechange = processReqChange;
req.open("GET", url, true);
req.send();
}
}
}
function processReqChange() {
if(req.readyState==4){
if(req.status==200){
if(req.responseText=='OK'){
document.getElementById('saveButton').style.visibility='visible';
document.getElementById('ajaxConsole').innerHTML='';
clearInterval(kaTimer);
kaTimer=setInterval(keepAlive, 30000);
}else{
document.getElementById('ajaxConsole').innerHTML = 'LOCKED: ' + _
req.responseText;
if(document.getElementById('ajaxConsole').innerHTML.substr(0,8) _
== 'LOCKED: ') {
clearInterval(kaTimer);
}
}
}else{
alert('Problem: [' + req.status + '] ' + req.statusText);
clearInterval(kaTimer);
}
req.onreadystatechange = new function(){};
}
}
function activateEditing() {
document.getElementById('saveButton').style.visibility='visible';
document.getElementById('ajaxConsole').innerHTML='';
clearInterval(kaTimer);
kaTimer=setInterval(keepAlive, 30000);
}
window.onload=initPage();
With this code, I've set up three functions: initPage(), keepAlive(), and processReqChange(). Your own Ajax code will need functions very much like these. The window.onload=initPage(); starts the ball rolling.
First, let me paint a little picture of what the rest of this page looks like. It's an article-editing screen, with buttons to Save, Preview, and Publish. The ID for the Save button is "saveButton". Near the top of the screen I've added a div that looks like this:
<div id="ajaxConsole"><TMPL_UNLESS NAME="STATUS_DRAFT">Do not edit this article! Wait until this text either disappears or is replaced by a "locked" message.<br/>It shouldn't take more than a couple of seconds. If you do not have Javascript enabled, you will not be able to edit an article in 'Pending' or 'Publish' status.</TMPL_UNLESS></div>
Article comments
1 - Aaman
I wish that Ajax book was cheaper:)
Incidentally, is this true AJAX, does the reliance on PHP and SQL not mean a new paradigm, not reliant on XML?
2 - Phillip Winn
It's still XMLHttpRequest, so all three elements of AJAX are present. The PHP and Mysql are, I think, incidental. It could as easily be anything else, or an external webservice, on the "back end."