jquery ajax results message

I have a ajax call to a php script that updates my MySQL DB with a new record when the user submits a data string as an entry. Part of the PHP is an if/else in place that will check to see if the entry is a duplicate. I can stop the duplicate from updating the database but I don't know how to send back an "error" message that says "That record already exists"...here is my jquery: [script] $(function() {

    $(".entry_button").click(function() 
{
    var element = $(this);
    var boxval = $("#entry").val();
    var dataString = 'entry='+ boxval;
        if(boxval=='') {
            alert("Please Enter Some Text");
        } else {

            $("#flash").show();
            $("#flash").fadeIn(400).html('<img src="images/loading.gif" align="absmiddle">&nbsp;<span class="loading">Broifying It...</span>');
            $.ajax({
                    type: "POST",
                    url: "update_data.php",
                    data: dataString,
                    cache: false,
                    success: function(html){
                        $("ol#update").prepend(html);
                        $("ol#update li").slideDown("slow");
                        document.getElementById('entry').value='';
                  开发者_运维知识库      $("#flash").hide();
                    }

            });
        }
        return false;
    });
});
[/script]

and here is my php script that updates the DB (update_data.php):

[php]
include('db.php');
if(isset($_POST['entry']))
{
$date_created = date('Y-m-d H:i:s');
$entry = $_POST['entry'];
$query = "SELECT COUNT(*) AS count FROM table WHERE entry = '$entry'";
$result = mysql_query($query);
$row = mysql_fetch_array($result);
if ($row['count'] == 0) {
mysql_query("insert into table (entry,date_created) values     ('$entry','$date_created')");
$sql_in= mysql_query("SELECT entry,id FROM table order by id desc");
$r=mysql_fetch_array($sql_in);
$newentry=$r['newentry'];
$id=$r['id'];
?>
<li class="entry bar<?php echo $id; ?>">
<div class="thebro"><span><?php echo $newentry; ?></span></div>
<div class="hr"></div>
<div class="utility-left"><span class="share"><a href="#" title="Share">share</a></span> | <span class="time">days ago</span></div>
<div class="utility-right"><span class="comments">COMMENTS</span> | <span  class="like">LIKE</span></div>
</li>
<?php
} else {
$error = "Sorry, that record already exists";
}   

}
[/php]

I want to be able to spit that $error variable from the php script to be sent back in the ajax call and be displayed in a element in my HTML. I've googled the crap out of ajax error messages but they all have to do with header errors, not validation error messages. I also am not using json_encode, unless someone wants to redo that jquery chunk above so that it is sent as json data.

Any ideas would be awesome!

---

If an error is produced in PHP, I want it to be handled by the error method of the jquery ajax object, and not 'fake it' by sending a normal HTTP 200 response with some error marking the responseText.

When a HTTP 500 is returned from PHP, no 'responseText' is captured by the ajax error handler. The error handler receives the XHR object, a status of 'error', and an error message of 'Internal Server Error'.

I tried to manipulate the error message..

header( 'HTTP/1.1 500 My Custom Error Message' );

But that didn't work.

What did work is this:

function errorHandler( $number, $message, $file, $line ) {
    $data = array(
        'message' => $message,
        'line' => $line,
        'file' => $file,
        'trace' => debug_backtrace()
    );

    header( 'Debug: ' . json_encode( $data, true ) );
}

This will get PHP to return HTTP 500, with your custom details in an extra header.

To access the custom details from the ajax error handler:

$.ajax({
    success: function( response ) {
        // ...
    },
    error: function( XHR, status, errorThrown ) {
        $.each( XHR.getAllResponseHeaders().split( '\n' ), function( i, header ) {
            if ( header.substr( 0, 7 ) == 'Debug: ' ) {
                var error = JSON.parse( header.substr( 7 ) );
                console.log( error );
            }
        });
    }
});

---

Just echo it in your phpfile and use:

document.getElementById('ajaxCatchbox').innerHTML = ajaxRequest.responseText;

The responsetext from your ajaxrequest object picks up everything thats echoed... Dunno the equivalent in jquery tho

---

Echo the error in PHP and exit. Then, at the beginning of your success: function, do something like this:

    if(ajaxRequest.responseText.substring(0, 5) === 'Sorry') {
        alert(ajaxRequest.responseText);
        return;
    }

I suggest using the substring approach because it allows you to create a variety of different error messages as long as they all begin with "Sorry". Useful for debugging.