php infinite loop and comet?

Question

Something seems wrong with my php script, but I have no idea what it is. The only possible thing that seems to be wrong is something to do with the cache, but I am not sure. Here's my script, I'll tell you what's happened below the code:

<?php
set_time_limit(0);
header('Content-Type:text/event-stream');
$prevmod=$lastmod=filemtime('chattext.txt');
function waitformod(){
global $lastmod;
global $prevmod;
while($prevmod==$lastmod){
    usleep(100000);
    clearstatcache();
    $lastmod=filemtime('chattext.txt');
    }
echo 'data:'.file_get_contents('chattext.txt').PHP_EOL.PHP_EOL;
flush();
$prevmod=$lastmod;
}
while(true){
waitformod();
}
?>

This is supposed to be used with the JavaScript EventSource and send the contents of chattext.txt whenever it is modified. The file does not output anything, however. I think it is because of the infinite loop. Is there any way to fix this?

This happens: 1) I modify the file 2) The php file sends chattext.txt as it was before I modified the file. Does that make more sense? — markasoftware
– markasoftware, Commented Jul 30, 2012 at 5:12

drew010 · Accepted Answer · 2012-07-30 05:16:51Z

1

Does something like this work better?

<?php

set_time_limit(0);
header('Content-Type:text/event-stream');

$prevmod = $lastmod = filemtime('chattext.txt');

function waitformod(){
    global $lastmod;
    global $prevmod;

    while($prevmod == $lastmod) {
        usleep(100000);
        clearstatcache();
        $lastmod = filemtime('chattext.txt');
    }

    echo 'data:'.file_get_contents('chattext.txt').PHP_EOL.PHP_EOL;
    flush();

    $prevmod = $lastmod;
}

while(1) {
    waitformod();
}

Your current code looks like it reads the file, outputs it, waits for it to change, and then terminates.

answered Jul 30, 2012 at 5:16

drew010

70.3k11 gold badges144 silver badges174 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

markasoftware Over a year ago

This seems great! Just asking (it's not important) what does flush() do in this case? I've heard of it but don't know what it does.

drew010 Over a year ago

It (tries) to force the server to flush the output buffer and send all data to the client at that time. Output is often buffered and doesn't get send immediately.

markasoftware Over a year ago

It looked like this would work, but it doesn't output anything. I think it is the infinite loop. How can I fix this?

Collectives™ on Stack Overflow

php infinite loop and comet?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related