Calling ob_flush() and flush(), yet browser doesn't show any output until script finishes

Question

Hi Please View Below Code :

<?php
ob_start();

echo "Start ...<br />\n";
for( $i = 0 ; $i < 10 ; $i++ )
{
    echo "$i<br />\n";
    ob_flush(); 
    flush();
    sleep(1);
}
echo "End ...<br />\n";
?>

It's Incorrect ? i'm tested it but my output show when script is done, have any solution ?

Have you tested this in multiple browsers? Removing `ob_start()` might be one piece of the puzzle, but you might also need to do something similar to what Jürgen suggested if it still doesn't work in IE. — , Apr 24 '11 at 14:53
Tested it on FireFox 4, IE9, IE8, IE8, IE6, Chrome . all of theme doesen't work — DJafari, Apr 24 '11 at 14:58
Hm, just a wild guess, but do you have mod_gzip active for the mime type of your script? — Jürgen Thelen, Apr 24 '11 at 15:02
Just want to make that sure: in your `php.ini` you've set `output_buffering = On`, and **not** to a value (e.g. `output_buffering = 4096`), `zlib.output_compression = Off` and no panel or `.htaccess` file does overwrite this values? — Jürgen Thelen, Apr 24 '11 at 15:26
tested [this](http://www.php.net/manual/en/function.flush.php#85382) with LAMP and firefox 4 IE8 Chrome, only work in IE8 — hope_is_grim, Apr 24 '11 at 15:28
@Jürgen Thelen : Checked, all of theme is ok . i'm wondering from this problem ! — DJafari, Apr 24 '11 at 15:41
@hope_is_grim, i have'nt LAMP, but doesn't must difrent width LAMP and WAMP — DJafari, Apr 24 '11 at 15:43
@Davood Jafari: Sorry, now I'm running out of ideas.. :( EDIT: you don't have a proxy between client and server, haven't you? — Jürgen Thelen, Apr 24 '11 at 15:56
@Davood Jafari: Another thing came to my mind: maybe your Apache is using modules that buffer output by themselves. You could try disabling Apache modules one by one to see if a specific module is causing the problem. — Jürgen Thelen, Apr 24 '11 at 16:44
Were you able to solve this? I seem to have run into this problem too. — om_deshpande, Aug 02 '13 at 07:37

score 14 · Answer 1 · answered Jun 12 '13 at 13:15

Hey man I was also got stuck in this problem and finally got the correct solution here it is for you

you have to add content type for your page you can do that by two ways 1. using html tag

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

Ex.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Wp Migration</title>
</head>
<body>
<?php 
for($i=0;$i<70;$i++)
{
echo 'printing...<br>';
ob_flush();
flush();
sleep(3);
}
?>
</body>
</html>

using php header function

<?php header( 'Content-type: text/html; charset=utf-8' ); ?>

Ex.

<?php 
header( 'Content-type: text/html; charset=utf-8' );
for($i=0;$i<70;$i++)
{
echo 'printing...<br>';
ob_flush();
flush();
sleep(3);
}
?>

All the best

So it seems the browser gets the content with or without the content type line, however if you don't have it, the browser simply changes the loading indicator to "receiving data" without displaying anything. Once you send the content type first, sending any amount of data and flushing will work =))) I confirmed the same behavior exists when running on Apache and IIS (regardless of output buffering settings) so it's definitely due to the browser's own requirements. — Yavor, Feb 19 '15 at 20:41

Jürgen Thelen · Answer 2 · 2011-04-24T15:37:56.330

Some browsers need to receive at least 256 characters before they start to render. Have you already tried to stuff more output like:

echo str_repeat('&nbsp;', 50) . "$i<br />\n";

EDIT:

Under Apache/2.2.11 (Win32) DAV/2 mod_ssl/2.2.11 OpenSSL/0.9.8i PHP/5.2.9 I was able to reproduce the problem of the OP by setting

zlib.output_compression = On

Turning it off again by

zlib.output_compression = Off

made the script work as wanted.

score 4 · Answer 3 · answered Apr 24 '11 at 14:04

4

Try removing the call to ob_start() on your first line : there is no need for you to enable output buffering -- and it probably causes troubles, here.

I've tested your code :

If ob_start() is called on the first line, I only see the output when the script finishes, after 10 seconds
If I remove that call to ob_start(), then, I see one line of output every second, as soon as it's displayed on the standard output.

answered Apr 24 '11 at 14:04

Pascal MARTIN

395,085
80
655
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If you remove `ob_start()`, then you should remove all the `ob_` calls as well. – Jason McCreary Apr 24 '11 at 14:10
Not sure about that *(If I remove the call to `ob_flush()`, I only see the output after the 10 seconds delay)* ; maybe it's because `output_buffering` is enabled in my php.ini, though ;;; see what's written on http://fr.php.net/flush too – Pascal MARTIN Apr 24 '11 at 14:13
are you sure ? tested in browser ? – DJafari Apr 24 '11 at 14:14
is possible give me link to view result ? – DJafari Apr 24 '11 at 14:19
I tested on my local computer *(and the Apache I've got on it is not accessible from the Internet)* ;; anyway, I just copy-pasted your code, and commented the `ob_start()` call. – Pascal MARTIN Apr 24 '11 at 14:22
I Tested it on local ( WAMP5 ) and Apache Web Server, both return output after 10 second ! i even tested this code on 2 server, but problem still exist . – DJafari Apr 24 '11 at 14:25

score 2 · Answer 4 · answered May 24 '12 at 18:14

2

Using Chrome, I found out that many more bytes are required to by-pass the browser's buffer. In my case 4096 bytes was fine:

echo str_repeat(' ', 4096);

Also, adding some HTML element at the beginning also seemed to be mandatory:

echo $content . '<br />';

answered May 24 '12 at 18:14

Matthias Noback

126
2

Probably better example is here: http://php.net/manual/en/function.flush.php#54841 – TomaszKane Mar 13 '15 at 15:46

score 1 · Answer 5 · answered Feb 05 '15 at 13:10

I've discovered that this was due to Apache's gzip compression being in use for my case.

To turn gzip off for the 'flushing' script only, I created a new .htaccess file in the directory where the continuous output script resides, with the following:

<IfModule mod_env.c>
    SetEnv no-gzip 1
</IfModule>

Flushing is working as expected again.

score 1 · Answer 6 · answered Feb 13 '15 at 07:22

1

For people using FCGI / fast cgi.

FcgidOutputBufferSize 0

answered Feb 13 '15 at 07:22

Alex S

147
2
3

score 1 · Answer 7 · edited Jun 17 '11 at 14:44

1

On my system it appears that FF4 needs more than 256 bytes to start rendering what is arriving from the server side, then i resolved with this at the beginning:

while (@ob_end_flush());
echo(str_repeat(' ',1024));
// ...etc...

edited Jun 17 '11 at 14:44

DarthJDG

16,511
11
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answered Jun 16 '11 at 14:52

Ulix

11
1

score 0 · Answer 8 · answered Aug 07 '13 at 08:48

0

One sneaky issue with IE8 and flush(); is that if you're "flushing" out rows in a table. IE will only display tables when they're complete. This was my issue, and changing containers from table rows to divs solved the problem.

answered Aug 07 '13 at 08:48

Kristian Sandström

764
5
10

score 0 · Answer 9 · edited Nov 28 '15 at 02:45

0

You need to add a .htaccess file to disable gzip output

<IfModule mod_env.c>
    SetEnv no-gzip 1
</IfModule>

edited Nov 28 '15 at 02:45

Mi-Creativity

9,554
10
38
47

answered Nov 28 '15 at 02:17

Dylan B

796
8
16

score 0 · Answer 10 · answered Aug 20 '16 at 19:07

I am using laravel framework and buffering did not work but. This is solution :

header( 'Content-type: text/html; charset=utf-8' );
ob_start();

ob_end_flush();
ob_flush();
flush();
for($i = 1;$i<= 5;$i++){
    echo $i;
    ob_flush();
    flush();

    sleep(3);
}

You have to use first ob_end_flush();

score 0 · Answer 11 · answered Mar 22 '17 at 06:41

0

This flow works with Laravel too

ob_implicit_flush(true);
echo "Processing ... "; // Or give out JSON output
ob_flush();
sleep(5); //A time-consuming synchronous process (SMTP mail, maybe?)
echo "Done";

answered Mar 22 '17 at 06:41

Deepak Thomas

3,355
4
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score 0 · Answer 12 · answered Apr 24 '11 at 14:08

0

It is correct. Works fine for me from CLI running PHP 5.3.3. If it's not working for you, your PHP install may have output buffering disabled.

I would also suggest putting ob_end_flush() at the end of your script to close the output buffer.

answered Apr 24 '11 at 14:08

Jason McCreary

71,546
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In Command Line Interface Worked, But Browser ... ! and output buffering is enable on my server :( – DJafari Apr 24 '11 at 14:13
i have ob_end_flush() in place – rinchik Feb 26 '13 at 15:33

Calling ob_flush() and flush(), yet browser doesn't show any output until script finishes

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