How do I close a connection early?

The following PHP manual page (incl. user-notes) suggests multiple instructions on how to close the TCP connection to the browser without ending the PHP script:

• Connection handling ^Docs

Supposedly it requires a bit more than sending a close header.

OP then confirms: yup, this did the trick: pointing to user-note #71172 (Nov 2006) copied here:

Closing the users browser connection whilst keeping your php script running has been an issue since [PHP] 4.1, when the behaviour of register_shutdown_function() was modified so that it would not automatically close the users connection.

sts at mail dot xubion dot hu Posted the original solution:

<?php
header("Connection: close");
ob_start();
phpinfo();
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();
sleep(13);
error_log("do something in the background");
?>

Which works fine until you substitute phpinfo() for echo('text I want user to see'); in which case the headers are never sent!

The solution is to explicitly turn off output buffering and clear the buffer prior to sending your header information. Example:

<?php
ob_end_clean();
header("Connection: close");
ignore_user_abort(true); // just to be safe
ob_start();
echo('Text the user will see');
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush(); // Strange behaviour, will not work
flush(); // Unless both are called !
// Do processing here 
sleep(30);
echo('Text user will never see');
?>

Just spent 3 hours trying to figure this one out, hope it helps someone :)

Tested in:

• IE 7.5730.11
• Mozilla Firefox 1.81

Later on in July 2010 in a related answer Arctic Fire then linked two further user-notes that were-follow-ups to the one above:

• Connection Handling user-note #89177 (Feb 2009)
• Connection Handling user-note #93441 (Sep 2009)

You can use Fast-CGI with PHP-FPM to use the fastcgi_end_request() function. In this way, you can continue to do some processing while the response has already been sent to the client.

• example of how to use fastcgi_finish_request() (Nov 2010)

You find this in the PHP manual here: FastCGI Process Manager (FPM); But that function specifically is not further documented in the manual. Here the excerpt from the PHP-FPM: PHP FastCGI Process Manager Wiki:

fastcgi_finish_request()

Scope: php function

Category: Optimization

This feature allows you to speed up implementation of some php queries. Acceleration is possible when there are actions in the process of script execution that do not affect server response. For example, saving the session in memcached can occur after the page has been formed and passed to a web server. fastcgi_finish_request() is a php feature, that stops the response output. Web server immediately starts to transfer response "slowly and sadly" to the client, and php at the same time can do a lot of useful things in the context of a query, such as saving the session, converting the downloaded video, handling all kinds of statistics, etc.

fastcgi_finish_request() can invoke executing shutdown function.

Note: fastcgi_finish_request() has a quirk where calls to flush, print, or echo will terminate the script early.

To avoid that issue, you can call ignore_user_abort(true) right before or after the fastcgi_finish_request call:

ignore_user_abort(true);
fastcgi_finish_request();

A better solution is to fork a background process. It is fairly straight forward on unix/linux:

<?php
echo "We'll email you as soon as this is done.";
system("php somestuff.php dude@thatplace.com >/dev/null &");
?>

You should look at this question for better examples:

PHP execute a background process

Assuming you have a Linux server and root access, try this. It is the simplest solution I have found.

Create a new directory for the following files and give it full permissions. (We can make it more secure later.)

mkdir test
chmod -R 777 test
cd test

Put this in a file called bgping.

echo starting bgping
ping -c 15 www.google.com > dump.txt &
echo ending bgping

Note the &. The ping command will run in the background while the current process moves on to the echo command. It will ping www.google.com 15 times, which will take about 15 seconds.

Make it executable.

chmod 777 bgping

Put this in a file called bgtest.php.

<?php

echo "start bgtest.php\n";
exec('./bgping', $output, $result)."\n";
echo "output:".print_r($output,true)."\n";
echo "result:".print_r($result,true)."\n";
echo "end bgtest.php\n";

?>

When you request bgtest.php in your browser, you should get the following response quickly, without waiting about 15 seconds for the ping command to complete.

start bgtest.php
output:Array
(
    [0] => starting bgping
    [1] => ending bgping
)

result:0
end bgtest.php

The ping command should now be running on the server. Instead of the ping command, you could run a PHP script:

php -n -f largejob.php > dump.txt &

Hope this helps!

You could try to do multithreading.

you could whip up a script that makes a system call ( using shell_exec ) that calls the php binary with the script to do your work as the parameter. But I don't think that is the most secure way. Maybe you can thighten stuff up by chrooting the php process and other stuff

Alternatively, there's a class at phpclasses that do that http://www.phpclasses.org/browse/package/3953.html. But I don't know the specifics of the implementation

Your problem can be solved by doing some parallel programming in php. I asked a question about it a few weeks ago here: How can one use multi threading in PHP applications

And got great answers. I liked one in particular very much. The writer made a reference to the Easy Parallel Processing in PHP (Sep 2008; by johnlim) tutorial which can actually solve your problem very well as I have used it already to deal with a similar problem that came up a couple of days ago.

Ok, so basically the way jQuery does the XHR request, even the ob_flush method will not work because you are unable to run a function on each onreadystatechange. jQuery checks the state, then chooses the proper actions to take (complete,error,success,timeout). And although I was unable to find a reference, I recall hearing that this does not work with all XHR implementations. A method that I believe should work for you is a cross between the ob_flush and forever-frame polling.

<?php
 function wrap($str)
 {
  return "<script>{$str}</script>";
 };

 ob_start(); // begin buffering output
 echo wrap("console.log('test1');");
 ob_flush(); // push current buffer
 flush(); // this flush actually pushed to the browser
 $t = time();
 while($t > (time() - 3)) {} // wait 3 seconds
 echo wrap("console.log('test2');");
?>

<html>
 <body>
  <iframe src="ob.php"></iframe>
 </body>
</html>

And because the scripts are executed inline, as the buffers are flushed, you get execution. To make this useful, change the console.log to a callback method defined in you main script setup to receive data and act on it. Hope this helps. Cheers, Morgan.

An alternative solution is to add the job to a queue and make a cron script which checks for new jobs and runs them.

I had to do it that way recently to circumvent limits imposed by a shared host - exec() et al was disabled for PHP run by the webserver but could run in a shell script.

Couldn't get any of the above to work with IIS but:

With all its limitations, the built in PHP -S webserver comes to the rescue.

Caller script (IIS)

//limit of length required!
<?php
$s = file_get_contents('http://127.0.0.1:8080/test.php',false,null,0,10);
echo $s;

Worker script (built in webserber @ 8080 - beware single thread):

ob_end_clean();
header("Connection: close");
ignore_user_abort(true);
ob_start();
echo 'Text the user will see';
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush(); // All output buffers must be flushed here
flush();        // Force output to client
// Do processing here 
sleep(5);
file_put_contents('ts.txt',date('H:i:s',time()));
//echo('Text user will never see');

Ugly enough? :)