PHP buffered output depending on server setting?

Question

I'm using the following code to produce buffered output on a db maintenance script:

function flush_buffers($string){
    echo $string;
    ob_end_flush();
    ob_flush();
    flush();
    ob_start();

}

While this works as expected on my local Wamp server, showing output each time the function is invoked, it doesn't on the online web server: here the output is sent only once the script has ended. How is that?

Does your web server have any additional buffering outside/beyond PHP's control? I believe that IIS, for example, commonly does this. — Wiseguy
– Wiseguy, Commented Jun 17, 2011 at 12:37
Netcraft reports: "Apache mod_fcgid/2.3.5 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 " — Riccardo
– Riccardo, Commented Jun 17, 2011 at 12:41
@dqhendricks, flush() manual states that some server overrides could occur :-( @Wiseguy, see second comment on flush() php manual (by user "brudinie") — Riccardo
– Riccardo, Commented Jun 17, 2011 at 12:44

Abs · Accepted Answer · 2011-06-17 13:40:31Z

4

Make sure output buffering is off in your php.ini file on your web server.

You also don't have to flush manually every time, you can make use of:

ob_implicit_flush(true);
ob_end_flush();

You should also remember that this is still browser specific. The browser will decide whether to show the output. Some browsers (for example IE6) won't output anything until it has enough characters to output.

The following will turn off everything that could cause unwanted output buffering.

@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);

edited Jun 17, 2011 at 13:40

answered Jun 17, 2011 at 12:54

Abs

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7 Comments

Riccardo Over a year ago

@Abs, same browser on two servers: one working, one not. Will ask the admin to check the settings in the PHP.ini file. Thanks

Abs Over a year ago

@Riccardo - you can do a quick test.php scrip where you just make use of phpinfo() and you can look for the output_buffering directive in your browser.

Riccardo Over a year ago

@Abs, has no settings: output_buffering "no value, no value"

Abs Over a year ago

@Riccardo and what is it set as for your WAMP server? Btw, there is a great comment in php.net by mandor. I have updated my question with it.

Riccardo Over a year ago

@Abs, this is correct. @Jarrod, it used to work on the production server, then due to resources usage limitation, it may have been turned off.

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