Long polling server loop - php

Question

I am trying to make a notification system of incoming messages. For examlpe user stays on the page and he recieves in a block that he has 2 unread messages.
My client code:
(function getmess(){
var id = '<?=$MY_ID;?>';
$.ajax({
url:"notif.php",
data:{"id":id,},
type:"GET",
success: function(result){
$("#count").html(result);
}, dataType: "json",
complete: getmess,
timeout: 10000});
})();
My server code:
<?php
$mysqli = new mysqli('localhost', 'root', '', 'lc');
if (mysqli_connect_errno()) {
printf("error: %s\n", mysqli_connect_error());
exit;
}
$MY_ID = $_POST['id'];
while (true) {
$result = $mysqli->query("SELECT COUNT(*) FROM messages WHERE user_get='$MY_ID' AND status='0' ");
if (mysqli_num_rows($result)) {
while ($row = mysqli_fetch_array($result)) {
echo $row[0]."";
}
exit;
}
sleep(5);
}
Everything works, but I have the problem that ajax requests are sent every 1 second and the lengh of these request is 1 second, and they overload the server.
I want to wait for a response from the server for at least 10 seconds in the case of a successful response to immediately send a new request, as well if the server does not respond within 10 seconds, ie in the database there is no change, then send a new query length of 10 seconds.
I think that is something wrong with server (may be sever loop), but i dont know how to improve this.

Answer 1

I'm sorry to say this is not going to work because for every user, your server has an open thread. That's going to get real heavy really fast.
It would be better to just poll the server ie. once per minute, and then have the server handle that request only once and not keep it open.
It is possible though, just not with PHP. Check out http://cometd.org/ for example.

Answer 2

Although there are other options available, if you go with polling, there are a few things you need to fix:
Don't use an interval for your polling, instead use a timeout that you set in the success function of the ajax request. That way you don't have to worry about requests overlapping.
As the javascript is doing the polling, don't use a loop in your php to poll for new database entries. Just check once and return the outcome to the browser.
Note that no change in the database is a normal, successful database
query so you can just send back an empty result. I would return json
with a list of database entries or an empty list if none are found and process these results in javascript.
In short, just do a quick check in your database in php and handle the rest in javascript.