Salve, ho questo script che praticamente ogni tot secondi, 30 per ora, richiama un file sul server.
Vorrei fare in modo che:
1- lo script generi il minor numero di richieste possibili al server, a me basta che richiami il file ogni 30 sec.
2- fare in modo che tipo dopo 1 ora si autodisabiliti e non aggiorni più la pagina.
3- se il file sul server non cambia nell'arco di 5 min, lo script si disabilita.

Codice PHP:
<script type="text/javascript">
<!--
var timeout;
function callReadFile(file_name) {
    readFileDoFunction(file_name, "GET", 
        function() {
            if(request.readyState == 4) {
                if(request.status == 200) {
                    var last_modified = request.getResponseHeader("Last-Modified");
                    var last_modified_date = new Date(last_modified);
                    displayResults(request.responseText, file_name, last_modified_date.getDate());
                }
            }
        }
    );
}
function readFileDoFunction(file_name, read_type, the_function) {
    if(window.XMLHttpRequest) {
        request = new XMLHttpRequest();
    } else {
        request = new ActiveXObject("Microsoft.XMLHTTP");
    }
    var the_url = "http://www.server.com/time/read_file.php?fileName=" + file_name + "&t=" + new Date().getTime();
    var the_results;
    if(request) {
        request.open(read_type, the_url);
        request.onreadystatechange = the_function;
        request.send(null);
    } else {
        alert("Devi aggiornare il browser prima di vedere il risultato della funzione AJAX ");
    }
}
function displayResults(the_results, file_name, last_modified) {
    document.getElementById("content").innerHTML = the_results;
    timeout = setTimeout("callUpdateIfChanged("+last_modified+",'"+file_name+"')",30000);
}
function callUpdateIfChanged(current_last_modified, file_name) {
    readFileDoFunction(file_name, "HEAD",
        function() {
            if(request.readyState == 4) {
                if(request.status == 200) {
                    var last_modified = request.getResponseHeader("Last-Modified");
                    var last_modified_date = new Date(last_modified).getTime();
                    if(last_modified_date != current_last_modified) {
                        callReadFile(file_name);
                    }
                    timeout = setTimeout("callUpdateIfChanged("+last_modified_date+",'"+file_name+"')",30000);
                }
            }
        }
    );
}
function stopTimer() {
    clearTimeout(timeout);
}


function updateClock () {
      var currentTime = new Date();

      var currentHours = currentTime.getHours();
      var currentMinutes = currentTime.getMinutes();
      var currentSeconds = currentTime.getSeconds();
      var msec = currentTime.getMilliseconds();
      currentMinutes = ( currentMinutes < 10 ? "0" : "" ) + currentMinutes;
      currentSeconds = ( currentSeconds < 10 ? "0" : "" ) + currentSeconds;
      var currentTimeString = currentHours + ":" + currentMinutes + ":" + currentSeconds;
      var currentChrono = currentHours + ":" + currentMinutes + ":" + currentSeconds;
      document.getElementById("chronotime").firstChild.nodeValue = currentChrono;
    }
//-->
</script>
</head>
<body onload="setInterval('updateClock()', 10 );callReadFile('http://www.server.com/file.txt');"> 
Grazie 1000

ciao

neorf