Question

I’m currently working on a lock/unlock feature for editing articles using a webfrontend.
As a reliable technique to unlock articles after editing, closing the brower or leaving the page I developed the following concept:

1. Lock the article when accessing the edit page
2. Immediately send an AJAX request without timeout to the unlock action

The unlock action has the following code. It is supposed to do nothing until the ajax request has been canceled.

ignore_user_abort(true);
set_time_limit(0);

while (!connection_aborted()) {

    usleep(100000);
}

// do database operations to unlock the article

but after the ajax request has been cancelled by ie. leaving the page, it never leaves the while-loop. I also tried this to test for an aborted connection:

while (connection_status() === CONNECTION_NORMAL)

but with the same result, it will never leave the loop.

Answer 1

Quote taken from the PHP Manual

PHP will not detect that the user has aborted the connection until an attempt is made to send information to the client. Simply using an echo statement does not guarantee that information is sent, see flush().

So in your while loop you should send dummy data to the client:

ignore_user_abort(true);
set_time_limit(0);

while (!connection_aborted()) {
    echo "null"; @flush(); @ob_flush();
    usleep(100000);
}

// do database operations to unlock the article