(PHP 4, PHP 5, PHP 7, PHP 8)
flush — Flush system output buffer
Flushes the system write buffers of PHP and the backend used by PHP (e.g.: CGI, a web server). In a command line environment flush() will attempt to flush the contents of the buffers only whereas in a web context headers and the contents of the buffers are flushed.
Note: flush() may not be able to override the buffering scheme of the web server and it has no effect on any client-side buffering in the browser.
Note: This function does not have any effect on user level output handlers such as those started by ob_start() or output_add_rewrite_var().
flush() can interfere with output handlers that set and send headers in a web context (e.g. ob_gzhandler()) by sending headers before these handlers can do so.
This function has no parameters.
No value is returned.
| Version | Description |
|---|---|
| 8.4.0 | Flushing headers without a body will now succeed in FastCGI. |
This will show each line at a time with a pause of 2 seconds.
(Tested under IEx and Firefox)
<?php
if (ob_get_level() == 0) ob_start();
for ($i = 0; $i<10; $i++){
echo "<br> Line to show.";
echo str_pad('',4096)."\n";
ob_flush();
flush();
sleep(2);
}
echo "Done.";
ob_end_flush();
?>This is what I use to turn off pretty much anything that could cause unwanted output buffering and turn on implicit flush:
<?php
@apache_setenv('no-gzip', 1);
@ini_set('zlib.output_compression', 0);
@ini_set('implicit_flush', 1);
for ($i = 0; $i < ob_get_level(); $i++) { ob_end_flush(); }
ob_implicit_flush(1);
?>
If it still fails though, keep in mind that Internet Explorer and Safari have a 1k buffer before incremental rendering kicks in, so you'll want to output some padding as well.If you want to make flush work when using php-fpm from Apache httpd with mod_proxy_fcgi, since 2.4.31 you can append flushpackets=on to enable flushing, which is instant by default, and and flushwait=n where n is in milliseconds to delay the flushing time for performance seconds.
These values can be appended to the <Proxy> directive, e.g. <Proxy "fcgi://localhost/" flushpackets=on flushwait=500> or in ProxyPass and ProxyPassMatch lines.
The mod_proxy_fcgi documentation for 2.4 does not document this, but it is available in the 2.5 or trunk documentation.I would like to point out that there is a function to replace ob_flush and flush. If you set ob_implicit_flush(true); at the top of the page it will automatically flush any echo or print you do in the rest of the script.
Note that you still need a minimum amount of data to come through the browser filter. I would advice using str_pad($text,4096); since this automatically lenghtens the text with spaces to 4 KB which is the minimum limit when using FireFox and linux.
I hope this helps you all out a bit.Regarding buffering by browser you can use:
$out=str_pad($yourMessage.'<br/>',1024);
print($out);
ob_flush();
flush();
Works for me in Firefox 60 ESR.For a Windows system using IIS, the ResponseBufferLimit takes precedence over PHP's output_buffering settings. So you must also set the ResponseBufferLimit to be something lower than its default value.
For IIS versions older than 7, the setting can be found in the %windir%\System32\inetsrv\fcgiext.ini file (the FastCGI config file). You can set the appropriate line to:
ResponseBufferLimit=0
For IIS 7+, the settings are stored in %windir%\System32\inetsrv\config. Edit the applicationHost.config file and search for PHP_via_FastCGI (assuming that you have installed PHP as a FastCGI module, as per the installation instructions, with the name PHP_via_FastCGI). Within the add tag, place the following setting at the end:
responseBufferLimit="0"
So the entire line will look something like:
<add name="PHP_via_FastCGI" path="*.php" verb="*" modules="FastCgiModule" scriptProcessor="C:\PHP\php-cgi.exe" resourceType="Either" responseBufferLimit="0" />
Alternatively you can insert the setting using the following command:
%windir%\system32\inetsrv\appcmd.exe set config /section:handlers "/[name='PHP_via_FastCGI'].ResponseBufferLimit:0"When using PHP with mode CGI/FastCGI there is a new buffer (initiated by mod_fcgid with a default size of 65536 bytes). That causes `flush()` and `ob_flush()` not working as expected with implicit_flush(true).
Setting "OutputBufferSize 0" in mod_fcgid config resolves the issue.
Hope it helps !Hi all.
Been scratching my head over data NOT flushed to IE (6) even though I tried strpad 4096 chars, all headers OK, TABLE and no TABLE, flush and ob_flush - still a blank page. Tried adding a sleep(1) before flushing - and everything worked as a charm.
/MikaelAfter searching through the PHP site, google and various forums, not finding a solution to my script not outputting anything while calling flush and ob_flush, I thought of trying to tell PHP to call:
session_write_close();
before starting echo'ing. It worked like a charm. I couldn't find any references to this, so I hope this note will help someone in the future.Like IE, Safari needs a fair amount of data before it'll display anything, actually more than explorer. The following code works for me in Firefox and Safari, and should work in IE as well.
<?php
for($i = 0; $i < 40000; $i++)
{
echo ' '; // extra spaces
}
// keeps it flowing to the browser?
flush();
// 50000 microseconds keeps things flowing in safari, IE, firefox, etc
usleep(50000);
?>
This code came from a comment on a blog discussing browser functionality with flush();If flush() function does not work. You must set next options in php.ini like:
--[code]--
output_buffering = Off
;output_handler =
zlib.output_compression = Off
;zlib.output_handler =
--[^code^]--
If things does not work you must view headers from the server and check `Server` string.
In my case, as the frontend was Nginx webserver and Apache work as backend.
Accordingly, buffering must be disabled in Nginx config file.
To stop buffering you must add next string to config file:
--[code]--
proxy_buffering off;
--[^code^]--
and restart Nginx daemon. More information about configuration you find in documentation on the nginx website.combining some ideas i was finally able to get a long running script to give me real time feedback on what it was doing. this was a wamp setup with php running as cgi. i'm pretty sure that apache just wasn't sending any of the buffered output because it was trying to be helpful. also trying to be helpful, i hope this example solution helps someone.
<?php
// thx mandor at mandor
ini_set('max_execution_time', 0);
ini_set('implicit_flush', 1);
ob_implicit_flush(1);
echo 'doing something'; my_flush();
sleep(5);
echo 'doing something else'; my_flush();
sleep(5);
echo 'finally done - hooray';
function my_flush() {
// following matt at hevanet's lead
for ($i=0;$i<10000;$i++) echo ' ';
ob_flush();
flush();
}I had a bunch of problems trying to get flush working on my windows box, I finally found a solution after reading everyones here and it not working.
1) Set output_buffering = 0
2) Set zlib.output_compression = 0
I then used Wireshark to monitor network packets, and indeed the server was pusing the data, but the browser was not displaying it.. So it was a browser buffer issue (I am on Firefox 13)
For me I needed to send about 1k of data before it would display the data. To do this I added more header information..
In php.ini I set default_charset = "utf-8"
And that was enough to give me enough for the buffer issue.
You can also try doing
echo str_repeat(" ", 1024), "\n";
at the start of the script.
hope this helpsThis is an extention of Rusty's comment below:
After sitting here for hours trying to make IE6 flush data out in the middle of a page (with it working perfectly in Firefox), I finally figured out the problem. IE will not display flushed data (even if it has it) unless the table that contains it is complete.
Every new element you want IE to display must not be in ANY kind of table at all. You must end all your tables.It is a bit complicated to work with the funktion flush() and you have to experiment with it a bit.
So if you design a site which has a timeloop at the end that calls a other site via a form data input (Data Submit) you have
to give something out to the buffer to get that new site loaden quick.
For example:
<?php
$instant=gettimeofday();
$timenow=$instant["sec"];//Start Time
//timeloop(e.g. for security_save after 30 min)
while (1) { echo "<b></b>";//Useless (only to quickload next
//or same Site when do a switch)
flush(); //giveout buffer
$instant=gettimeofday();
$timeactual=$instant["sec"]; //get Actual Time in Secs
$flag=(($timeactual>$timenow+$diff)? 1:0);//$diff=switchTime
if ($flag) { what_do_at_switch_Time();//Sec.Save etc.etc.
$timenow=$timeactual; } //Set new Start Time
sleep(5); //Or so...(Important)
} //End of while-Loop
?>
So you can programm a security save or other function in your site and if you do a switch the upload of the new or same site (the called site) works...I've spent days trying to figure out why flush didn't work all of a sudden, while it used to work perfectly. Apparently, it was McAfee Spamkiller that caused problems. Disabling it didn't work, I had to completely remove it. Hope this helps someone.If you're not explictly using the buffering functions, then ob_flush() is only necessary if output buffering is turned on in your php.ini file.
flush() is only necessary if implicit_flush is turned off in your php.ini file. Setting implicit_flush to on will remove the need for all these flush() calls, but it's generally only good in an extremely controlled environment. Turning on implicit_flush in a production environment can be bad.This helped me getting flushing to work.
Using apache with deflate.
Turning compression off for this script: (add it somewhere at the top of the script)
apache_setenv('no-gzip', '1');
However, this only works if php is running as a module rather than a cgi-extension and safe mode must be disabled.
You can also turn the compression off for a directory by making a .htaccess file and adding the following entry:
mod_gzip_on Off
However that affects the whole directory.
Hope I could help.on php8.3-fpm with apache 2.4.57
In order flush to work in the browser you need to send some more data (at least 4096 bytes / flush) and you need to add a setting for that site to the virtual host of your apache2 configuration:
<FilesMatch \.php$>
SetHandler "proxy:unix:/run/php/php8.3-fpm.sock|fcgi://localhost"
</FilesMatch>
<Proxy fcgi://localhost/">
ProxySet enablereuse=on flushpackets=on
</Proxy>Hello,
I had the same problems with sending a javascript after the <body></body> content has been sent to the browser (the script updates the content of an iframe).
Two solutions work for me:
- add enough data (i.e.: extra dummy text like spaces) or,
- echo the '</body>' tag at the end of the page
Note, that for the latter to work one should:
- turn of output_buffering in php.ini and either:
* turn on implicit_flush in its php.ini or,
* call ob_implicit_flush(); at the beginning of a script
I preferr echoing the '</body>' tag at the end as it doesn't require any extra data to be sent over the wire and its much a neater coding technique.
Notes:
- these worakarounds aren't needed when using perl and cgi,... .
- you can leave the zlib.output_compression in your php.ini switched on
Kind regards and hoped this is of any help.
MauritsI figured out a way to create a simple progress bar that is for the most part cross platform. Seeing as I got my ideas from this site it's only share to give back to the community.
Note: Something interesting about browser buffering... you have to have the <html><body> for Firefox and some other browsers to recognize items by their id in Javascript. So I recommend using some sort of header function before calling this function.
<?php
function fn_progress_bar($intCurrentCount = 100, $intTotalCount = 100)
{
static $intNumberRuns = 0;
static $intDisplayedCurrentPercent = 0;
$strProgressBar = '';
$dblPercentIncrease = (100 / $intTotalCount);
$intCurrentPercent = intval($intCurrentCount * $dblPercentIncrease);
$intNumberRuns++;
if(1 == $intNumberRuns)
{
$strProgressBar = <<< BAR
<table width='50%' id='progress_bar' summary='progress_bar' align='center'><tbody><tr>
<td id='progress_bar_complete' width='0%' align='center' style='background:#CCFFCC;'> </td>
<td style='background:#FFCCCC;'> </td>
</tr></tbody></table>
<script type='text/javascript' language='javascript'>
function dhd_fn_progress_bar_update(intCurrentPercent)
{
document.getElementById('progress_bar_complete').style.width = intCurrentPercent+'%';
document.getElementById('progress_bar_complete').innerHTML = intCurrentPercent+'%';
}
</script>
BAR;
}
else if($intDisplayedCurrentPercent <> $intCurrentPercent)
{
$intDisplayedCurrentPercent = $intCurrentPercent;
$strProgressBar = <<< BAR
<script type='text/javascript' language='javascript'>
dhd_fn_progress_bar_update($intCurrentPercent);
</script>
BAR;
}
if(100 <= $intCurrentPercent)
{
$intNumberRuns = $intDisplayedCurrentPercent = 0;
$strProgressBar = <<< BAR
<script type='text/javascript' language='javascript'>
document.getElementById('progress_bar').style.visibility='hidden';
</script>
BAR;
}
echo $strProgressBar;
flush();
ob_flush();
}
?>Regarding Apache2
flush() will produce the same results as ob_flush() when output buffering is involved.