Ciao.
Esempio pagina HTML:
Codice PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<
html xmlns="http://www.w3.org/1999/xhtml">
<
head>
<
meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<
title>Our wonderful AJAX page!</title>
<
script language="javascript" type="text/javascript">
function 
DOMize(element
{
/////
/// DOMize function by andr3a Utente di HTML.it
////
    
if(!element.addEventListener)
    {
        
element.addEventListener=function(event,listener)
                                {
                                    
event="on"+event;
                                    if(
this.attachEvent)
                                    {    
                                        
this.attachEvent(event,listener);
                                    }
                                    else 
                                    {            
                                        
this[event]=listener;
                                    }
                                 }

    };
    if(!
element.removeEventListener)
    {
        
element.removeEventListener=function(event,listener)
                                    {
                                        
event="on"+event;
                                        if(
this.detachEvent)    
                                        {
                                            
this.detachEvent(event,listener);
                                        }
                                        else     
                                        {        
                                                
delete this[event];
                                        }
                                    }
    };
    return 
element;
};
function 
getPage(){

var 
xmlhttp=false//Clear our fetching variable
        
try {
                
xmlhttp = new ActiveXObject('Msxml2.XMLHTTP'); //Try the first kind of active x object…
        
} catch (e) {
                try {
                        
xmlhttp = new
                        
ActiveXObject('Microsoft.XMLHTTP'); //Try the second kind of active x object
            
} catch (e) {
                
xmlhttp false;
                        }
        }
        if (!
xmlhttp && typeof XMLHttpRequest!='undefined') {
                
xmlhttp = new XMLHttpRequest(); //If we were able to get a working active x object, start an XMLHttpRequest
        
}

        var 
file 'query.php?page=';
         
//This is the path to the file we just finished making *
        
var sel document.getElementsByTagName("select")[0];
        var 
whatinfo sel.options[sel.selectedIndex].value;
        
xmlhttp.open('GET'file whatinfotrue); //Open the file through GET, and add the page we want to retrieve as a GET variable **
        
xmlhttp.onreadystatechange=function() {
        if (
xmlhttp.readyState==4) { //Check if it is ready to recieve data
                
var content xmlhttp.responseText//The content data which has been retrieved ***
                
if( content ){ //Make sure there is something in the content variable

            
if(test document.getElementById("paragraph")) {
            
document.getElementById("target").removeChild(test);
            }
                var 
info document.createElement("p");
                
info.setAttribute("id""paragraph");
                var 
text document.createTextNode(content);
                
info.appendChild(text);
                
document.getElementById("target").appendChild(info);
            }
        }
        }
        
xmlhttp.send(null//Nullify the XMLHttpRequest
return;
}
window.onload = function()
{
var 
sel document.getElementsByTagName("select")[0];
DOMize(sel).addEventListener("change",getPagefalse); 
}

</script>
</head>
<body>
<form method="get">
<select name="choosepage">
<option  value="">Choose page</option>
<option  value="uno">Page One</option>
<option value="due">Page Two</option>
</select>
</form>
<div id="target"></div>
</body>
</html> 
Pagina PHP:
Codice PHP:
<?php 
//This file is text.php
 
mysql_connect("localhost"""""); //Connect to the mysql server with your host (most likely localhost), username, and password
mysql_select_db(""); //Select your database by name
 
$page $_GET["page"]; //This is the variable we retrieve through GET to know which row of content to retrieve
 
$sql "SELECT * FROM pages WHERE page = '$page'"//This is the text of the query. We will select the content field from the table ‘pages’ where the page field has the same value as the one we want to retrieve
 
$query mysql_query($sql) or die(mysql_error()); //Make the actual query
 
if( mysql_num_rows($query) == //Check to see if we found 1 row with that page name
{
  
$r=mysql_fetch_assoc($query); //Set a mysql fetching variable for the query
  
echo $r["content"]; //Echo out the content of the page we want
}
else
{
  echo 
"Sorry, that page was not found."//Otherwise, echo out an error message saying the page was not found
}

?>