Flushing output buffer

[steve_green]

I've just moved to Red Fox and my PHP scripts that flushed the output buffer to the browser on my old host now don't flush the output buffer until the whole script has finished processing.

I've set the following:

ini_set('output_buffering', 'On');

and I use these commands to flush the output buffer:

ob_flush();
flush();

Does anyone have any idea how I can get the output buffer to flush its contents to the browser before the script has finished all of its processing?

[RFH Reseller: nick]

I'm not entirely sure whether you can set output buffering with ini_set? That could possibly be a reason. To test you could just start the buffer with

ob_start(); 

before anything is output in your script.
I have flushed many a buffer with no problems on scripts run on redfox. The only problems I have ever come across involve using output buffer compression as there is an irritating known php bug on Windows.

[steve_green]

Hi, thanks for replying.

When I first ran one of my scripts that flushes the output buffer it produced an error with a link to this page of the PHP manual:

http://uk.php.net/outcontrol

That page prompted me to try

ini_set('output_buffering', 'On');

On my old host it was fine without using that line.

Does the following code flush the buffer every 2 seconds for you or does it wait until the whole script has finished processing:

<?php

if (ob_get_level() == 0) ob_start();

for ($i = 0; $i<10; $i++){

        echo "<br> Line to show.";
        echo str_pad('',4096)."\n";    

        ob_flush();
        flush();
        sleep(2);
}

echo "Done.";

ob_end_flush();

?>

I've just taken that from the PHP manual page for flush():

http://uk.php.net/manual/en/function.flush.php

For me it waits 20 seconds then outputs everything at once.

[RFH Reseller: nick]

Okay, yes I do get the same behaviour on RF, whereas locally (Apache 1.3, PHP5, OS X) the script is working correctly. Even more strangely, if we take output buffers out of the equation and run this script:

for ($i = 0; $i<10; $i++){
        echo "<br> Lines to show.";
        echo str_pad('',4096)."\n";    
        sleep(2);
}
echo "Done."; 

we get the same behaviour where everything is sent to the browser at the very end of execution rather than as things are echoed.

More investigation is certainly needed, but I wonder if Warren has any ideas?

[Staff: Warren Ashcroft]

I wonder if this has to do with the fact we run PHP in CGI mode as opposed to unstable ISAPI?

Maybe with CGI, it returns the data to IIS in one go as opposed to bit by bit?

[RFH Reseller: nick]

I wonder if this has to do with the fact we run PHP in CGI mode as opposed to unstable ISAPI?

Maybe with CGI, it returns the data to IIS in one go as opposed to bit by bit?

I found a bug that sounds like our problem, but it appears to have been fixed in the latest builds http://bugs.php.net/bug.php?id=34429.

[Staff: Warren Ashcroft]

I found a bug that sounds like our problem, but it appears to have been fixed in the latest builds http://bugs.php.net/bug.php?id=34429.

Thats definatly the bug here, but they say its been fixed on 18.12.05, we use 5.1.4 which was released on 04.05.06?

[RFH Reseller: nick]

Thats definatly the bug here, but they say its been fixed on 18.12.05, we use 5.1.4 which was released on 04.05.06?

Looking on Carbon it appears to be running 5.1.2

[Staff: Warren Ashcroft]

Looking on Carbon it appears to be running 5.1.2

Thats odd, my work log shows a PHP update to 5.1.4 a couple of weeks ago...

Anyway, I will get PHP updated tonight across all the web servers, hopefully it should resolve the buffer bug.

[steve_green]

That would be great, thanks very much.

One thing I noticed though is this:

http://uk.php.net/manual/en/function.flush.php

"Several servers, especially on Win32, will still buffer the output from your script until it terminates before transmitting the results to the browser.

Server modules for Apache like mod_gzip may do buffering of their own that will cause flush() to not result in data being sent immediately to the client."

I know very little about servers, so I may be barking up the wrong tree here, but could what it says above affect the behaviour anyway even if you update PHP tonight?