AJAX请求不起作用（POST）

Question

I have a little problem with a POST request using AJAX. The data just doesn't seem to get stored in the database. When I used GET instead of POST it worked, but the problem is that it sends a huge amount of data since it is imagedata from a canvas on the page. I tried to print out the size of the data that is sent to make sure it actually is correct before it is sent (it was about 10500 characthers long).

Here's the Javascript/AJAX-code:

if(type == "DrawingData" && Drawer)
{
    var CanvasData = canvas.toDataURL("image/png"); 
    var url = "DB_Com.php";
    var params = "DrawingData="+CanvasData;

    xmlhttp.open("POST", url, true);

    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.setRequestHeader("Content-length", params.length);
    xmlhttp.setRequestHeader("Connection", "close");

    xmlhttp.send(params);
}

And here is the PHP-code:

if(isset($_POST['DrawingData']))
{
    $Image = mysql_real_escape_string($_POST['DrawingData']);

    $query = "UPDATE BlackboardDrawing SET Data = '$Image'";
    mysql_query($query) or die(mysql_error());
}

Any help is is highly appreciated. Thanks!

Answer 1

Your Ajax looks fine, but you need to POST the row id that you are updating. :

if(type == "DrawingData" && Drawer)
{
    var CanvasData = canvas.toDataURL("image/png"); 
    var url = "DB_Com.php";
    var rowid = 'your_row_id';
    var params = "DrawingData="+CanvasData+"rowid="+rowid;

    xmlhttp.open("POST", url, true);

    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.setRequestHeader("Content-length", params.length);
    xmlhttp.setRequestHeader("Connection", "close");

    xmlhttp.send(params);
}

And change your PHP script:

if(isset($_POST['DrawingData']))
{
    $Image = mysql_real_escape_string($_POST['DrawingData']);
    $rowid = (int)$_POST['rowid'];
    $query = "UPDATE BlackboardDrawing SET Data = '$Image' WHERE id='$rowid'";
    mysql_query($query) or die(mysql_error());
}