Question

I have a variable localStorage.lastUpdate which stores a timestamp such as 1332237161. I need to pass that timestamp to the server which im trying to do by the line below with:

listener.php?q="+localStorage.lastUpdate

I also have another variable, localStorage.numUpdates that should receive the number of updates back from the server. I am confused whether I can use the below code with xml to run commands. Can my server side php file do something of the following

echo "localStorage.numUpdates=".$currentCount.";";

echo "localStorage.lastUpdate=".time().";";

where it would take affect on my localStorage variables in the javascript portion?

function contactServer()
{
    if (window.XMLHttpRequest){ xmlhttp=new XMLHttpRequest();}
    else{xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");}

    xmlhttp.onreadystatechange=function()
    {
        if (xmlhttp.readyState==4 && xmlhttp.status==200)
        {
            xmlhttp.responseText;
        }
    }
    xmlhttp.open("GET","listener.php?q="+localStorage.lastUpdate,true);
    xmlhttp.send();
}

Any information would be helpful, thanks!

Answer 1

That won’t work (and don’t use eval()!).

But you can just output JSON in your PHP script:

echo json_encode( array('lastUpdate' => time(), 'numUpdated' => $currentCount) );

And in your JavaScript code:

if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
  var result = JSON.parse(xmlhttp.responseText);
  localStorage["lastUpdate"] = result["lastUpdate"];
  localStorage["numUpdated"] = result["numUpdated"];
}