ob_flush

(PHP 4 >= 4.2.0, PHP 5)

ob_flush — Flush (send) the output buffer

说明

void ob_flush ( void )

This function will send the contents of the output buffer (if any). If you want to further process the buffer's contents you have to call ob_get_contents() before ob_flush() as the buffer contents are discarded after ob_flush() is called.

This function does not destroy the output buffer like ob_end_flush() does.

返回值

无返回值。

参见

ob_get_clean

ob_end_flush

Last updated: Sun, 25 Nov 2007

add a note User Contributed Notes
ob_flush

Jens
30-Oct-2008 11:01


If you call ob_flush() and flush() and still dont get the buffer flushed it might be because some antivirus software (Panda in this case) holds the buffer until the page has finished loaded before sending it to the browser.

Lucas
28-Aug-2008 06:13


I just had some problems with flush() and ob_flush(). What I did to resolve this problem took me some time to figure out so I'd like to share what I came up with.



The main problem is the php setting "output_buffering" which can be set too large and will prevent your text from outputting. To change this value you can either set it in php.ini or you can add the line 



php_value output_buffering "0"



to your .htaccess file. It will not work with ini_set() since it is PHP_INI_PERDIR.



Next thing is to begin with ob_start();

Then you need

ob_flush();

flush();

before any echo or print.



Your code might look like this:



<?php

ob_start();



for($i=0;$i<70;$i++)

{

    echo 'printing...<br />';

    ob_flush();

    flush();



    usleep(300000);

}



?>



Hope this helps anyone with the same problems.

colnector at@ colnect punto com
08-Jul-2008 07:35


As stated in flush() manual entry, if php compresses the ouput with zlib this function may be ineffective.



A possible option for folders on your server that have scripts which may take a long time to run is to add the following in your relevant .htaccess file:



<FilesMatch "\.(php|html?)$">

php_flag zlib.output_compression off

php_value max_execution_time 3000

php_value max_input_time 3000

</FilesMatch>

kel at no-spam dot newcastleinfotech dot com dot au
06-Jun-2008 12:33


Also note that any data in the buffer will flush at the end of the script, not destroyed, so it is often not necessary to call ob_flush(); for example:



<?php

ob_start();

echo 'Hello World!'

?>



Will still result in Hello World! being displayed to the browser.

matt at ihaventthefoggiest dot com
23-May-2008 03:25


Just to note, I don't think image output functions (imagejpeg, imagegif etc) are caught by ob. This code:

<?php

ob_start();

$im = imagecreateturecolor(100,20);

$white = imagecolorallocate($error_im,255,255,255);

$black = imagecolorallocate($error_im,0,0,0);

imagefttext($im,12,0,0,0,$black,'font.ttf','Hello, world!');

imagegif($im);

ob_flush();

?>

will still produce a black on white image saying "Hello, world!"

solidli at gmail dot com
24-May-2007 12:28


Use an '@' sign as "@ob_flush();" to avoid the following message:



Notice: ob_flush(): failed to flush buffer. No buffer to flush. in /etc/www/test.php on line 88

22-Sep-2005 09:37


I was having problems with output buffering which seemed to be active by default on the server, although phpinfo said something else..



In any case I needed to know that when I ran ob_start, it would start at the top level, so I could use ob_flush as it's intended without having to call multiple ob_flush in-script - this is what I did:



<?php



// make sure output buffering is off before we start it

// this will ensure same effect whether or not ob is enabled already

while (ob_get_level()) {

    ob_end_flush();

}

// start output buffering

if (ob_get_length() === false) {

    ob_start();

}



?>



Then I could call ob_flush(); followed by flush(); and get the output I wanted, which I didn't if I started the script with just ob_start();



This was on a windows apache 2 server with php 5.0.4 btw.

24-Jun-2005 09:27


You must call them in the correct order.

ob_flush();

flush();

Reynard Hilman
23-Jun-2005 05:29


when using command line php, if somewhere in your script you have ob_start(), you have to call ob_end_flush() first, and then you can call these functions: 

flush();

ob_flush();



without calling ob_end_flush first, flush and ob_flush does not have any effect, at least that's what I experienced.

jeremy at e2-media dot co dot nz
26-May-2005 07:09


we had problems with flushing data to the browser. a simple call to ob_flush() or flush() would not work. We found that repeatly calling theses fuctions did work however.



<?

flush();

ob_flush();

flush();

ob_flush();

flush();

ob_flush();

?>



go figure!

15-Jan-2003 12:23


As far as I can tell the only way to mimic ob_flush()'s behaviour on PHP < 4.2.0 is calling ob_end_flush() followed by ob_start().

add a note

ob_get_clean

ob_end_flush

Last updated: Sun, 25 Nov 2007