creating background processes in php for long running process

Question

Ok so forgive me if this is a repeat of another question, but after searching I have not found a clear answer. What I basically want to do is have my php web application fire off some event (like an emailer or report generator) that may take a few minutes to complete and immediately return control to the page. I come from a .NET world where this can easily be accomplished with a thread.

So here's the workflow:

User clicks 'generate Report' button
ajax call made to '../blah/generate-report' and returns immediately
process is started and runs until completion while the user can then go about his business
User can return to report page and see progress: "Report 50% complete"

What's the best way to accomplish this? Brief answers are fine. I don't want code written for me, just some guidance. I looked at shell_exec but I'm not sure exactly if that is the best way or if it is, how to use it to process functions within a web app. (I'm using the Yii framework if that makes any difference). Thanks.

-Jason

PHP is single-threaded. If you have the process control extension you can spawn additional PHP processes but they're not threads, par-se. Alternatively, you can `exec('/usr/bin/php name_of_script.php')` — GordonM, Feb 06 '14 at 14:31
To correct the above comment, there exists pthreads extension that exposes threading capabilities to developers. However, even with that you still wouldn't be able to serve HTML and do the background task since the web server process would hang until the PHP process is done, and it's done only when all the threads have completed. What you're looking for is to implement a job server or a task farm. Gearman comes to mind and might be of help. You populate a queue of a different process using a web request. Then you perform a different HTTP request to enquire about the job status. — N.B., Feb 06 '14 at 14:44
And another comment to correct my own :) if you are interested in any chance to work with threads, you could check out the repository I'll link along with [this example](https://github.com/krakjoe/pthreads/blob/master/examples/SimpleWebRequest.php) that shows you how to perform an async request, if that solves your problem (although the answer Drew provided handles that task with less hassle). — N.B., Feb 06 '14 at 14:57
@N.B. I'm aware of pthreads, but it's not a commonly used extension and has certain requirements that can make installing it problematic. — GordonM, Feb 06 '14 at 15:04

score 2 · Answer 1 · answered Feb 06 '14 at 14:49

2

The best (and only AFAIK) way to start a new ~~thread~~ thread like thing in PHP is to create a new PHP request using something like curl.

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, 'http://www.yoursite.com/background-script.php');
curl_setopt($ch, CURLOPT_FRESH_CONNECT, true);
curl_setopt($ch, CURLOPT_TIMEOUT_MS, 1);

curl_exec($ch);
curl_close($ch);

This will run the script, and immediately return the page. Of course there's no callback, so your best bet is to put the output of background-script.php into a database, and then ping the database every so often from the client until you see the results.

answered Feb 06 '14 at 14:49

Drew

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[Because using an actual thread would be bad?](https://github.com/krakjoe/pthreads) – N.B. Feb 06 '14 at 14:52
This just forwards the original request ie. it doesn't make it asynchronous. Ex: if the background-script.php doesn't repspond within 1st min any async request sent within the same session will wait until the background-script will send its response. What's asynchronous in that? – Eugen Mihailescu May 07 '16 at 11:16

Jan K. S. · Answer 2 · 2014-02-06T20:10:39.087

We've created a function here that returns an answer to the browser and keeps executing. We use it to send email without making the user wait for it.

public function redirectAndContinue( $url )
{
    ignore_user_abort(true);
    header("Location: $url");
    header("Connection: close");
    header("Content-Length: 0");
    flush();
}

You may use it like this

// do quick basic stuff to validate your report

$this->redirectAndContinue( $url )

// send your email or do other slow stuff

The problem is: it doesn't work with AJAX, it must be a regular page request (possibly with a POST). But you can make the progress bar anyway: save something in your database or session and then keep calling some URL to get the progress via AJAX.

score 1 · Answer 3 · answered Feb 06 '14 at 14:58

As far as I remember, shell_exec or exec will block the execution of your PHP script until the process will terminate. A solution is to append a "&" at the end of your command, your script/program will be backgrounded.

"/usr/report.sh &"

I have used something like that to run external tool from PHP, but passing by an intermediary script to control PID, number of instances... Can't say if it is working under Windows host.

score 0 · Answer 4 · answered Oct 24 '15 at 20:10

May I suggest Gearman? You can submit jobs to a gearman server and request the status.

Gearman provides a distributed application framework for work with multiple machines or processes. It allows applications to complete tasks in parallel, to load balance processing and to call functions between languages. The framework can be used in a variety of applications. Gearman is multi-threaded and is known to be able to carry out 50 thousand jobs per-second.

A quick tutorial is here: http://www.sitepoint.com/introduction-gearman-multi-tasking-php/

Its also quite easy to get started, and all your code will be in PHP.

creating background processes in php for long running process

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