Smart reloading

naiad

Hi:

I'm trying a php chat system... In the moment of conversation. I got two chat windows (me and customer ones)...

Each time somebody writes something, his window is reloaded and it's added to a common file called "conversation.html" the sentence he said.

To have the conversation updated, now i'm using the META REFRESH html tag to reload each window each 5 seconds.

But it's too busy to do this... 🙁

How can i say from one to another that somebody has written something ?

I thought about sessions... when one window writes something, it's reloaded, and the conversation file is updated. And the other window has a DO-WHILE watching when a variable of session has changed.

But maybe this overloads too much the PHP... or not ?

Any ideas ?

I've seen demos of phplive support systems... several of them uses the META REFRESH solution... and I saw one demo (located in http://www.phplivechat.com/demos/2.4/demonstration.htm) that only reloads the other page when someone has written something... how do they do ? 🙂

Thank you in advance

DigitalExpl0it

looks like all they do is

either

use frames and have the main window only refresh

have no refresh have the user hit submit then they are taken to another page where there is a php insert script then refreshed to the chat page very fast.. liek use META with a 0 refresh then it loosk like you just refreshed the page but you didnt..

chat.php -> insert.php - > chat.php

all in a blink of a eye 🙂

naiad

no...

if they do the second you told... of course is not necessary to do chat.php -> insert -> chat.php

you can place insert code at the top of chat.php, for example

if ($message) { insert into conversation file }
// and now the rest
show the conversation

I know that the correct is to put FRAMES... one for the FORM to input messages and other to show conversation.

But I repeat again... in the phpchat (I told URL)... they JUST reload the conversation when the other part has written something...

That is what i'm looking for...

A way to know in PHP when another php script has changed one file or something.

The first solution i see is a infinite DO WHILE checking some changes (in a file, in session vars)... but... can it overload the system too much ? would it be the solution ?

another one ?

Weedpacket

Even if you do have such a loop running in PHP, it will only serve the new page to the browser when the browser requests it. So there has to be something sitting on the user's computer ticking over and every now and then saying "Ooh! Time to refresh!" and sending back a request to see what's new.

Pretty much what you've got already.

There is a way to have the server "push" stuff out to the client instead of having the client "pull" stuff (a hack described here, which compares the two); but you'll have to consider the number of connections the server will have to keep open at any given moment to satisfy everyone.

[Edit: just a thought if you still have client-initiated refresh: how busy is the forum? If you maintained statistics on how often posts are made, you'll have a better idea when tuning the refresh rate - possibly to the extent of speeding up the refresh rate at busy times of the day. Of course, the refresh will happen anyway if the user actually asks for one (or posts).]

naiad

Hi:

In the phplive program I said, there's nothing on client-side... It's all server side. It's a pity I can't see the source code.

The idea of looping is not as you said... I meant this.

Window1: it has a loop (while-do) of when HTTP_SESSION_VARS["changed"] is for example = 1

Window2: the client writes something, it press enter, the page is reload, the PHP at the top of the script rewrites the conversation text file and it puts HTTP_SESSION_VARS["changed"] to 1
Then the Window1 will refresh inmediately...

Of course, this would extends to put that changed with a timestamp knowing the last time of somebody wrote, ect... but not the problem right now 🙂

The question is if that loop would consume or overload too much... something similar to

do { nothing } while $HTTP_SESSION_VARS["changed"]!=$last_time_somebody_wrote

Thank you

P.D. Then any idea of how can they do it ? (http://www.phplivechat.com/demos/2.4/demonstration.htm)

naiad

I have tried to see the code, but impossible 🙁

no ideas then ?

Weedpacket

Originally posted by naiad

But I repeat again... in the phpchat (I told URL)... they JUST reload the conversation when the other part has written something...

That just sounds like they're careful about putting an appropriate Last-Modified header in the response (eg, "Last-Modified: Sun, 06 Nov 1994 08:49:37 GMT"). When the browser requests the page from the server (or the proxy), the latter first responds with the headers (of course). If the Last-Modified date matches the one on the copy the browser's already got in its cache, then the browser doesn't bother with the rest of the request and just uses its cached copy.