AJAX刷新整个PHP页面

How to update all php data on my page? I have communication system and I need to refresh all php data to update chat messages, users statuses and more for example every 750 miliseconds. I think AJAX do it but I don't know how.

you can try this , it refreshes for every 750 secs generating random numbers for every 750 milli seconds

<html>
<head>
<script src="http://code.jquery.com/jquery-latest.js"></script>

<script>
$(document).ready(
 function() {
 setInterval(function() {
 var someval = Math.floor(Math.random() * 100);
  $('#sample').text('Test' + someval);
 }, 700);  //Delay here = 750 milliseconds 
});
</script>
</head>
<body>

<div id="sample">Testing refresh every 750 milliseconds</div>
</body>