libAjaxUtil.js
Codice PHP:
/*
 * Istanzia l'oggetto XMLHttpRequest
 */
 
function makeXMLHttpRequest()
{
    var request = undefined;
    if (window.XMLHttpRequest)
    {
        request = new XMLHttpRequest();
        if(request.overrideMimeType)
        {
            request.overrideMimeType("text/xml");
        }
    }else{
        if(window.ActiveXObject)
        {
            try
            {
            request = new ActiveXObject("Msxml2.XMLHTTP");
            }catch(e){
                try
                {
                    request = new ActiveXObject("Microsoft.XMLHTTP");
                }catch(e){}
            }
        }
    }
    return request;
} 
index.html
Codice PHP:
<html>
<head>
<script type="text/javascript" src="libAjaxUtil.js"></script>
</head>

<body>
<input type="text" id="input" />

<div id="content"></div>
<button onclick="javascript:change(document.getElementById('input').value)">change</button>
<script type="text/javascript">
/*
 * Callback delle richieste AJAX
 */
 
function ajaxCallback()
{
    
}
function change(n){
var xmlHttpRequest = makeXMLHttpRequest();
if(!xmlHttpRequest)
{
    alert('Non è possibile usare AJAX');
}else{
    xmlHttpRequest.onreadystatechange = function(){try
    {
        if(xmlHttpRequest.readyState == 4)
        {
            if(xmlHttpRequest.status == 200)
            {
                var text = xmlHttpRequest.responseText;
                var doc = xmlHttpRequest.responseXML;
                document.getElementById('content').innerHTML = text;
            }else{
                if(xmlHttpRequest.status == 404){alert('404: Not Found');}
                else if(xmlHttpRequest.status == 500){alert('500: Internal Server Error');}
                else{alert(xmlHttpRequest.status + ': '+ xmlHttpRequest.statusText);}
            }
        }else{}
    }catch(e){
        alert('Errore in callback function: '+ e);
    }};//ajaxCallback;
    xmlHttpRequest.open('GET','content.php?n='+n,true);
    xmlHttpRequest.send(null);
}}
</script>
</body>
</html> 
content.php
Codice PHP:
<?php
$n = $_GET['n'];
for($i=0; $i<$n; $i++)
{
    echo "ciao
";
}
?>
testato e funzionante.....