[jQuery] ifModified - status is "notmodified", although response isn't empty

[Sven Burkert]

Hello,

I send an request to a php file on the server:

$(document).ready(function(){
    updatePresenceBox();
    setTimeout("updatePresenceBox()", 3000);
    setTimeout("updatePresenceBox()", 6000);

});

function updatePresenceBox() {
    $.ajax({
        url: "test.php",
        dataType: "html",
        ifModified: "true",
        complete: function(data, status){ alert(status); },
        success: function(html) {alert("i'm successful");
$("#presence").html(html);  }
    });
}

The status is like I expected: First time "success", second and third  time
"notmodified". But in Firebug I see that the response contains always the
generated text ("test with php") from the php file (when I test this case
with a html file the response is empty).
Can someone please explain me why?

This is the code in my "test.php" file:

header("Last-modified: Thu, 01 Jan 2007 10:00:00 GMT");
echo "test with php";
exit;