flush() - why the heck isn't this working?

[Coastal Web]

Hey guys, any idea why this isn't working?
The output just dumps all to the browser, instead of 1 second increments as l would expect.

PHP Code:

<?

ob_end_flush();  
flush();

for($i=0;$i<5;$i++){
    echo 'test ' . $i . '<br />';
    flush();
    sleep(1);
}

?>

[Lamped]

There's a lot of buffering going on (gz handler, apache etc). Basically, this isn't going to ever work unless you have a very specific and unusual setup (and one that's far from optimal).

[tangoforce]

Then you get ISP caching...

Plus the socket buffer sizes on your computers OS.. there are so many different buffers between your browser and the script on the server that you'll never achieve the desired result. The only other thing you can do is to repeatedly call the script time and time again Not ideal but it would have the desired effect.. ish.

Basically, unless its a data stream, you can't use php for a live output. Thats because most socket buffers have a size of around 4Kb give or take a few.

[hinch]

remove / comment out

ob_start();
ob_end_flush();

etc if they appear anywhere

add this to a functions file or somewhere it can be referenced

PHP Code:

/** 
* Output buffer flusher
* Forces a flush of the output buffer to screen useful for displaying long loading lists eg: bulk emailers on screen 
* Stops the end user seeing loads of just plain old white and thinking the browser has crashed on long loading pages.
*/
function fcflush()
{
    static $output_handler = null;
    if ($output_handler === null) {
        $output_handler = @ini_get('output_handler');
    }
    if ($output_handler == 'ob_gzhandler') {
        // forcing a flush with this is very bad
        return;
    }
    flush();
    if (function_exists('ob_flush') AND function_exists('ob_get_length') AND ob_get_length() !== false) {
        @ob_flush();
    } else if (function_exists('ob_end_flush') AND function_exists('ob_start') AND function_exists('ob_get_length') AND ob_get_length() !== FALSE) {
        @ob_end_flush();
        @ob_start();
    }
} 


call your code

and replace flush() with fcflush();

PHP Code:

<?php

for($i=0;$i<5;$i++){
    echo 'test ' . $i . '<br />';
    fcflush();
    sleep(1);
}

?>

and for gods sake use proper php openings not short openings.

[tangoforce]

Originally Posted by hinch

add this to a functions file or somewhere it can be referenced

PHP Code:

/** 
* Output buffer flusher
* Forces a flush of the output buffer to screen useful for displaying long loading lists eg: bulk emailers on screen 
* Stops the end user seeing loads of just plain old white and thinking the browser has crashed on long loading pages.
*/
function fcflush()
{
    static $output_handler = null;
    if ($output_handler === null) {
        $output_handler = @ini_get('output_handler');
    }
    if ($output_handler == 'ob_gzhandler') {
        // forcing a flush with this is very bad
        return;
    }
    flush();
    if (function_exists('ob_flush') AND function_exists('ob_get_length') AND ob_get_length() !== false) {
        @ob_flush();
    } else if (function_exists('ob_end_flush') AND function_exists('ob_start') AND function_exists('ob_get_length') AND ob_get_length() !== FALSE) {
        @ob_end_flush();
        @ob_start();
    }
} 


Not that socket buffer sizes on a windows machine or an ISP can be overridden by PHP but you're still using flush() in your function - which as demonstrated already doesn't work.

Secondly I've just tried using it on my wamp setup and again, it doesn't work through a browser. I did however get it to work up to the 4th loop using a http debugging program.. which then froze. I tried another which did work upto and past 30 however no normal browser will work like this.

Finally if it doesn't work on localhost it certainly won't on a remote server with an ISP between it and the end user due to cache issues and socket buffers.

To put it mildly, your code is unstable.

[chris0]

as far as i know, the web browser do not display any part of the page untill it received the full file.

and the load images and js files

[hinch]

Originally Posted by tangoforce

To put it mildly, your code is unstable.

The code is very very stable and used in several very large scale commercial projects where its tried and tested. (This very forum uses exactly the same code snippet!)

Not only does it work perfectly on wamp servers but it also works perfectly on unix servers.

If a page flush isn't happening then there's some other issues at work which aren't browser/code related.

In usage you'd use it something like this.

PHP Code:

while (($data = fgetcsv($handle, 3000, ",")) !== FALSE) {
set_time_limit(60); //reset time limit to stop script timing out
echo "<span style=\"color:green\">$row - Importing Ticket ".$data[4]."</span> - ";
$row++;
//check if ticket already exists
$sql = "";
$result = mysql_query($sql) or die(mysql_error());
                    if (mysql_num_rows($result)>0) {
                        echo "Ticket Exists - Updating<br />";
                        $importsql = "";
                        mysql_query($importsql) or die(mysql_error());
                        fcflush();
                    } else {
                        $importsql = "";
                        mysql_query($importsql) or die(mysql_error());
                        echo "New Ticket - Inserting<br />";
                        fcflush();
                    }
                } 


[tangoforce]

hinch, I'd invite you to demonstrate it in use but to be honest, I've never once seen any flush call work successfully in a browser.

As I said, for some http based programs such as the one I used yesterday it may work but for webpages it does not.

[hinch]

i shall send you a PM to a small video