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:

1. User clicks 'generate Report' button
2. ajax call made to '../blah/generate-report' and returns immediately
3. process is started and runs until completion while the user can then go about his business
4. 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

Answer 1

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.

Answer 2

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.