PHP flush stopped flushing in IIS7.5

Question

We have been using php flush to \"blank\" a page immediately as soon as it is clicked, and also to send the navigation and main components of the page so that a page appears

Answer 1

Enter the following command as Administrator in Powershell:

C:\Windows\System32\inetsrv> .\appcmd.exe set config /section:handlers "/[name='PHP_via_FastCGI'].ResponseBufferLimit:0"

Expected Output:

Applied configuration changes to section "system.webServer/handlers" for "MACHINE/WEBROOT/APPHOST" at configuration comm it path "MACHINE/WEBROOT/APPHOST"

For more background, have a look at: http://www.coastrd.com/cgioniis7

Basically, we need to tell FastCGI to turn of its ResponseBufferLimit. This cannot be done through the IIS Management Console (checked only 7.5)

Answer 2

Here's another way of doing this with web.config (@Jules's method didn't work for me with IIS 8.0). Of course, you would want to replace the PHP versions and paths with the ones actually on your machine.

This allows the usage of server-sent events!

<configuration>
    <system.webServer>
        <handlers>
            <remove name="PHP53_via_FastCGI" />
            <remove name="PHP54_via_FastCGI" />
            <remove name="PHP55_via_FastCGI" />
            <add name="PHP53_via_FastCGI" path="*.php" verb="GET,HEAD,POST" type="" modules="FastCgiModule" scriptProcessor="C:\Program Files (x86)\PHP\v5.3\php-cgi.exe" resourceType="Either" requireAccess="Script" allowPathInfo="true" preCondition="" responseBufferLimit="0" />
            <add name="PHP54_via_FastCGI" path="*.php" verb="GET,HEAD,POST" type="" modules="FastCgiModule" scriptProcessor="C:\Program Files (x86)\PHP\v5.4\php-cgi.exe" resourceType="Either" requireAccess="Script" allowPathInfo="true" preCondition="" responseBufferLimit="0" />
            <add name="PHP55_via_FastCGI" path="*.php" verb="GET,HEAD,POST" type="" modules="FastCgiModule" scriptProcessor="C:\Program Files (x86)\PHP\v5.5\php-cgi.exe" resourceType="Either" requireAccess="Script" allowPathInfo="true" preCondition="" responseBufferLimit="0" />
        </handlers>
    </system.webServer>
 </configuration>

Answer 3

You must set the ResponseBufferLimit value of the desired handler to a number low enough to actually flush. I recommend using 0 since it prevents IIS from doing anything but passing along what you send it from your PHP script. You can use the following command line to set the ResponseBufferLimit to 0 for the php handler (just change “NAME” to the name of the handler you want to update e.g. PHP53_via_FastCGI):

appcmd.exe set config /section:handlers "/[name='NAME'].ResponseBufferLimit:0"

Alternatively, you can edit the applicationHost.config directly and add a ResponseBufferLimit attribute the XML element.

Answer 4

What I do is that I use the following function:

function flush_buffers(){
    ob_end_flush();
    ob_flush();
    flush();
    ob_start();
}

So in your code:

ob_start();
flush_buffers();

echo "starting...<br/>\n";
for($i = 0; $i < 5; $i++) {
    print "$i<br/>\n";
    flush_buffers();
    sleep(2);
}

It should work flawlessly :-)

---

Here is some working code (with correct Content-Type set):

<?php
header("Content-Type: text/html; charset=utf-8");
function flush_buffers(){
    ob_end_flush();
    ob_flush();
    flush();
    ob_start();
}

ob_start();
flush_buffers();
echo "starting...<br/>\n";
for($i = 0; $i < 60; $i++) {
    flush_buffers();
    print   "$i<br/>\n";
    flush_buffers();
    sleep(2);
}

flush_buffers();

print "DONE!<br/>\n";
?>

Answer 5

I'm a little late to the party, but thought I'd add how to do this with web.config.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
        <!--- other stuff here --->
        <handlers>
            <remove name="ISAPI-dll" />
            <add name="ISAPI-dll" path="*.dll" verb="*" type="" modules="IsapiModule" scriptProcessor="" resourceType="File" requireAccess="Execute" allowPathInfo="true" preCondition="" responseBufferLimit="0" />
        </handlers>
    </system.webServer>
</configuration>

Answer 6

It's up to the webserver whether it decides to naggle the content or send it via chunked encoding. So although PHP can ask the server to push data out to the client, it can't force the server to use chunked encoding.

This article suggests you explicitly need to set the transfer encoding for IIS (see the bit about ISAPI) for sending data to the server - you might try the same in your script.

IME, most scenarios where this is an issue can be better dealt with by....

register_shutdown_function('do_slow_stuff');
....generate html content....
exit; // closes stdin/stdout, but shutdown fn will still be called 

function do_slow_stuff()
{
  ....
}