How do I 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( '[email protected]', "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.

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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

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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

It's necessary to send these 2 headers:

Connection: close Content-Length: n (n = size of output in bytes ) 

Since you need know the size of your output, you'll need to buffer your output, then flush it to the browser:

// buffer all upcoming output ob_start(); echo 'We\'ll email you as soon as this is done.';  // get the size of the output $size = ob_get_length();  // send headers to tell the browser to close the connection header('Content-Length: '.$size); header('Connection: close');  // flush all output ob_end_flush(); ob_flush(); flush();  // if you're using sessions, this prevents subsequent requests // from hanging while the background process executes if (session_id()) {session_write_close();}  /******** background process starts here ********/ 

Also, if your web server is using automatic gzip compression on the output (ie. Apache with mod_deflate), this won't work because actual size of the output is changed, and the Content-Length is no longer accurate. Disable gzip compression the particular script.

For more details, visit http://www.zulius.com/how-to/close-browser-connection-continue-execution