Best way to manage long-running php script?

Certainly it can be done with PHP, however you should NOT do this as a background task - the new process has to be dissociated from the process group where it is initiated.

Since people keep giving the same wrong answer to this FAQ, I've written a fuller answer here:

http://symcbean.blogspot.com/2010/02/php-and-long-running-processes.html

From the comments:

The short version is shell_exec('echo /usr/bin/php -q longThing.php | at now'); but the reasons "why", are a bit long for inclusion here.

Update +12 years

While this is still a good way to invoke a long running bit of code, it is good for security to limit or even disable the ability of PHP in the webserver to launch other executables. And since this decouples the behaviour of the log running thing from that which started it, in many cases it may be more appropriate to use a daemon or a cron job.

The quick and dirty way would be to use the ignore_user_abort function in php. This basically says: Don't care what the user does, run this script until it is finished. This is somewhat dangerous if it is a public facing site (because it is possible, that you end up having 20++ versions of the script running at the same time if it is initiated 20 times).

The "clean" way (at least IMHO) is to set a flag (in the db for example) when you want to initiate the process and run a cronjob every hour (or so) to check if that flag is set. If it IS set, the long running script starts, if it is NOT set, nothin happens.

You could use exec or system to start a background job, and then do the work in that.

Also, there are better approaches to scraping the web that the one you're using. You could use a threaded approach (multiple threads doing one page at a time), or one using an eventloop (one thread doing multiple pages at at time). My personal approach using Perl would be using AnyEvent::HTTP.

ETA: symcbean explained how to detach the background process properly here.

No, PHP is not the best solution.

I'm not sure about Ruby or Perl, but with Python you could rewrite your page scraper to be multi-threaded and it would probably run at least 20x faster. Writing multi-threaded apps can be somewhat of a challenge, but the very first Python app I wrote was mutlti-threaded page scraper. And you could simply call the Python script from within your PHP page by using one of the shell execution functions.

PHP may or may not be the best tool, but you know how to use it, and the rest of your application is written using it. These two qualities, combined with the fact that PHP is "good enough" make a pretty strong case for using it, instead of Perl, Ruby, or Python.

If your goal is to learn another language, then pick one and use it. Any language you mentioned will do the job, no problem. I happen to like Perl, but what you like may be different.

Symcbean has some good advice about how to manage background processes at his link.

In short, write a CLI PHP script to handle the long bits. Make sure that it reports status in some way. Make a php page to handle status updates, either using AJAX or traditional methods. Your kickoff script will the start the process running in its own session, and return confirmation that the process is going.

Good luck.

I agree with the answers that say this should be run in a background process. But it's also important that you report on the status so the user knows that the work is being done.

When receiving the PHP request to kick off the process, you could store in a database a representation of the task with a unique identifier. Then, start the screen-scraping process, passing it the unique identifier. Report back to the iPhone app that the task has been started and that it should check a specified URL, containing the new task ID, to get the latest status. The iPhone application can now poll (or even "long poll") this URL. In the meantime, the background process would update the database representation of the task as it worked with a completion percentage, current step, or whatever other status indicators you'd like. And when it has finished, it would set a completed flag.

You can send it as an XHR (Ajax) request. Clients don't usually have any timeout for XHRs, unlike normal HTTP requests.

I have done similar things with Perl, double fork() and detaching from parent process. All http fetching work should be done in forked process.

Not the best approach, as many stated here, but this might help:

ignore_user_abort(1); // run script in background even if user closes browser
set_time_limit(1800); // run it for 30 minutes

// Long running script here

If the desired output of your script is some processing, not a webpage, then I believe the desired solution is to run your script from shell, simply as

php my_script.php