Check if user closed the page in PHP?

I made a chat using PHP and JavaScript chat and there is a disconnect button which removes user from the chat removing him from user list first. But if the user closes browser then he will remain in the user list. How do I check if he left?

This must be done without putting any handles on page closing in JS because if user kills the browser then he will remain in chat.

By the way , JS script always sends a request to the PHP page which constantly checks for new mess开发者_如何学Cages in a loop and when there are some, the script prints them out and exits. Then it repeats all over again.

EDIT : How do I make a heartbeat thing in PHP? If a user closes the page the script execution will be terminated therefore we won't be able to check if the user is still connected in the same script.

Sorry, there is no reliable way of doing this, that's the way HTTP was built - it's a "pull" protocol. The only solution I can think of is that "valid" and logged in clients must query the server in a very small interval. If they don't, they're logged out.

you could send a tiny ajax call to your server every 5 seconds. and users that doesn't do this aren't in the room any more

You answered your own question: if you don't detect a request for new messages from a user over a given length of time (more than a few seconds), then they left the room.

The nature of HTTP dictates that you need to do some AJAX type of communication. If you don't want to listen for the "give me more messages" request (not sure why you wouldn't want to), then build in a heartbeat type communication.

If you can't modify the JS code for some reason, there really is little you can do. Only thing you can do with PHP is to check if there's been for example over 15 minutes from the last activity, the user has left. But this is in no way a smart thing to do – a user might just sit and watch the conversation for 15 minutes.

Only proper way to do is using AJAX polling in set intervals if you want to do it reliably.

You noted that a user polls the server for new messages constantly, can't you use that to detect if user has left?

Maintain a list of active users on the server, as well as the last time they connected to the chat to request new messages.

When a user connects to check for messages update their time.

Whenever your code runs iterate through this list and remove users who haven't connected in too long.

The only failure is that if the number of users in the channel drops to zero, the server wont notice until someone comes back.

To address your edit, you can ignore client termination by using ignore_user_abort.

Using javascript u can do the following :

<script type="text/javascript">

window.onunload = unloadPage;

function unloadPage()
{
 alert("unload event detected!");
}
</script>

Make the necessary ajax call on the unloadPage() function to ur PHP Script

Request a PHP script that goes a little something like this, with AJAX:

register_shutdown_function("disconnect_current_user");
header('Content-type: multipart/x-mixed-replace; boundary="pulse"');

while(true) {
   echo "--pulse\r\n.\r\n";
   sleep(2);
}

This way, you won't constantly be opening/closing connections.

The answers to all the questions asked by the OP are covered in the section in the manual about connection handling:

http://uk3.php.net/manual/en/features.connection-handling.php

No Ajax.

No Javascript.

No keep alives.

C.