close a connection early

Question

I'm attempting to do an AJAX call (via JQuery) that will initiate a fairly long process. I'd like the script to simply send a response indicating that the process has started, but JQuery won't return the response until the PHP script is done running.

I've tried this with a "close" header (below), and also with output buffering; neither seems to work. Any guesses? or is this something I need to do in JQuery?

<?php

echo( "We'll email you as soon as this is done." );

header( "Connection: Close" );

// do some stuff that will take a while

mail( '[e-mail]', "okay I'm done", 'Yup, all done.' );

?>

Answer 1

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)

Answer 2

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!

Answer 3

this worked for me

//avoid apache to kill the php running
ignore_user_abort(true);
//start buffer output
ob_start();

echo "show something to user1";
//close session file on server side to avoid blocking other requests
session_write_close();

//send length header
header("Content-Length: ".ob_get_length());
header("Connection: close");
//really send content, can't change the order:
//1.ob buffer to normal buffer,
//2.normal buffer to output
ob_end_flush();
flush();
//continue do something on server side
ob_start();
//replace it with the background task
sleep(20);

Answer 4

I'm on a shared host and fastcgi_finish_request is setup to exit scripts completely. I don't like the connection: close solution either. Using it forces a separate connection for subsequent requests, costing additional server resources. I read the Transfer-Encoding: cunked Wikipedia Article and learned that 0\r\n\r\n terminates a response. I haven't thoroughly tested this across browsers versions and devices, but it works on all 4 of my current browsers.

// Disable automatic compression
// @ini_set('zlib.output_compression', 'Off');
// @ini_set('output_buffering', 'Off');
// @ini_set('output_handler', '');
// @apache_setenv('no-gzip', 1);

// Chunked Transfer-Encoding & Gzip Content-Encoding
function ob_chunked_gzhandler($buffer, $phase) {
    if (!headers_sent()) header('Transfer-Encoding: chunked');
    $buffer = ob_gzhandler($buffer, $phase);
    return dechex(strlen($buffer))."\r\n$buffer\r\n";
}

ob_start('ob_chunked_gzhandler');

// First Chunk
echo "Hello World";
ob_flush();

// Second Chunk
echo ", Grand World";
ob_flush();

ob_end_clean();

// Terminating Chunk
echo "\x30\r\n\r\n";
ob_flush();
flush();

// Post Processing should not be displayed
for($i=0; $i<10; $i++) {
    print("Post-Processing");
    sleep(1);
}

Answer 5

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.

Answer 6

Complete version:

ignore_user_abort(true);//avoid apache to kill the php running
ob_start();//start buffer output

echo "show something to user";
session_write_close();//close session file on server side to avoid blocking other requests

header("Content-Encoding: none");//send header to avoid the browser side to take content as gzip format
header("Content-Length: ".ob_get_length());//send length header
header("Connection: close");//or redirect to some url: header('Location: http://www.google.com');
ob_end_flush();flush();//really send content, can't change the order:1.ob buffer to normal buffer, 2.normal buffer to output

//continue do something on server side
ob_start();
sleep(5);//the user won't wait for the 5 seconds
echo 'for diyism';//user can't see this
file_put_contents('/tmp/process.log', ob_get_contents());
ob_end_clean();