How to execute ajax function onbeforeunload?

Question

I'm developing a php/javascript chat.

When the user logs in, his/her username is inserted in a MySQL table called queue. This insert returns the mysql_insert_id() that will be stored in a session variable called $_SESSION['CHAT_QUEUE_ID']

I need the MySQL table row to be deleted when the user closes the page.

I tried the following, but without success:

js file

window.onbeforeunload = closeSession;
function closeSession(){
    $.ajax({
        url: "/chat/process/chat.php",
        type: "GET"
    });
    return "disconnected";
}

chat.php

$delete= "DELETE FROM queue WHERE id = " . $_SESSION['CHAT_QUEUE_ID'];
// query, etc

Is there any way to do this?

Are you aware that browser support for ``onbeforeunload`` is limited? E.g. opera doesn't support it. — ckruse, Mar 14 '12 at 12:17
The common method is to define a timeout. If a user hadn't had an activity for a specific amount of time he is disconnected. — ckruse, Mar 14 '12 at 12:52

StilgarBF · Accepted Answer · 2013-12-17T07:42:44.337

21

You fire your ajax async (default for jquery - ajax). But the browser won't wait for anything on unload.

try setting async : false in the ajax-settings. But you can never be sure that this will work in all browsers everytime.

see the comment here: http://api.jquery.com/unload/#dsq-comment-body-132164390

edited Dec 17 '13 at 07:42

answered Mar 14 '12 at 12:21

StilgarBF

1,060
8
17

It works perfectly. should have thought of that before... THANKS! – matheusvmbruno Mar 14 '12 at 12:46
2

Also - if you are triggering the same functional ajax call that you use asynchronously (or a number of ajax calls) you can set them to async globally in your onbeforeunload statement: $.ajaxSetup({ async: false }); – JSP64 Oct 12 '13 at 22:37
A useful followup on setting async=false to reset to async=true: http://stackoverflow.com/a/4651049/449444 – René Dec 05 '14 at 09:36
Do you know why we have to set it to be synchronous ? As what we want is to send data to the server but don't care about server response since the data is passed ? – TOPKAT Jun 20 '16 at 12:35

How to execute ajax function onbeforeunload?

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