CODEWITHSUNDEEP
phpjavascript
Jamie
Jamie

Reputation: 379

Need a simple way to repeatedly poll a file using javascript

Hopefully the below is close, but I feel I'm doing the first part wrong.

Ideal outcome is status-remote.php to be polled every 2 seconds, while not being cached (hence the random nocache variable).

If it's relevant, the php file has two variables the status of which determines the visibility on this page.

<script id="status" type="text/javascript"></script>

<script type="text/javascript">
  var nocache = Math.random();
    setInterval(
     document.getElementById('status').src = '/status-remote.php?sid=2&random='+nocache;
     }, 2000);
</script>

Thanks so much for taking a look!

Upvotes: 1

Views: 1293

Answers (4)

Alfred
Alfred

Reputation: 61793

Cache:

(hence the random nocache variable)

I think you are filling up the users browser cache with a lot of crap this way. You should sent correct headers to bypass caching instead(also better for proxies).

//Set no caching
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");

Pick one:

Sidenote:

The performance/scalability is (probably) going to suck(especially if the load is NOT in memory). I think if you could you should really avoid polling. Some solutions to prevent this:

Upvotes: 0

CAFxX
CAFxX

Reputation: 30331

You could use a (hidden) iframe and have status-remote.php return an html document with a meta header:

<meta http-equiv="refresh" content="2" />

then parse the response via javascript in the main document.

edit: To prevent caching, I'd suggest sending the appropriate HTTP headers.

edit2: I somehow missed that it's an http-equiv meta header, so you can send an HTTP refresh header instead. 

Refresh: 2; url=http://www.example.com/

This also means that you're not bound to send HTML content. Also, in the HTTP you can specify a delay and the URL to go to (in case you really want to go with the status-remote?random=random_number cache-preventing thingy)

Upvotes: 1

Oralet
Oralet

Reputation: 347

I think you should call Math.random() inside the setIntervalmethod.
Something like this:

<script type="text/javascript">
   setInterval("var nocache = Math.random();
   document.getElementById('status').src = 
   '/status-remote.php?sid=2&random='+nocache;", 2000);

Upvotes: 1

macarthy
macarthy

Reputation: 3069

I would suggest using http://socket.io/ , it degrade to all browsers and uses the best available option using feature detection.

Upvotes: 0

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