Run a PHP-script from a PHP-script without blocking

Question

I'm building a spider which will traverse various sites and data mining them.

Since I need to get each page separately this could take a VERY long time (maybe 100 pages). I've already set the set_time_limit to be 2 minutes per page but it seems like apache will kill the script after 5 minutes no matter.

This isn't usually a problem since this will run from cron or something similar which does not have this time limit. However I would also like the admins to be able to start a fetch manually via a HTTP-interface.

It is not important that apache is kept alive for the full duration, I'm, going to use AJAX to trigger a fetch and check back once in a while with AJAX.

My problem is how to start the fetch from within a PHP-script without the fetch being terminated when the script calling it dies.

Maybe I could use system('script.php &') but I'm not sure it will do the trick. Any other ideas?

A friend told med about nohup, think that'll work? That is system('nohup php -f script.php &') — Nicklas Ansman
– Nicklas Ansman, Commented Mar 13, 2010 at 21:15

Erik · Accepted Answer · 2010-03-13 21:16:05Z

6

    $cmd = "php myscript.php $params > /dev/null 2>/dev/null &";

    # when we call this particular command, the rest of the script 
    # will keep executing, not waiting for a response
    shell_exec($cmd);

What this does is sends all the STDOUT and STDERR to /dev/null, and your script keeps executing. Even if the 'parent' script finishes before myscript.php, myscript.php will finish executing.

answered Mar 13, 2010 at 21:16

Erik

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9 Comments

Andy Over a year ago

don't forget to use php.net/manual/en/function.escapeshellarg.php on $params

symcbean Over a year ago

But it will fall on it's arse if the session terminates. And can no longer be signalled with a HUP (e.g. to stop gracefully). A better solution is to attach it to a different session header e.g. 'echo php myscript.php | at now'

symcbean Over a year ago

....and you would not believe how complicated and flaky Erik's suggestion will get if you launch it from apache.

Erik Over a year ago

@symcbean: What do you mean by "if the session terminates"? The calling script can end and the called script continues to run to completion.

Erik Over a year ago

@symcbean: I'd like to learn, so why dont you back up your comments? I've this identical piece of code running on a production site for a year .. it gets called 100+ times per hour and its never exhibited any problems.

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TeAmEr · Accepted Answer · 2010-11-15 07:54:25Z

1

if you don't want to use exec you can use a php built in function !

ignore_user_abort(true);

this will tell the script to resume even if the connection between the browser and the server is dropped ;)

answered Nov 15, 2010 at 7:54

TeAmEr

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2 Comments

patrick Over a year ago

this should be the selected answer

Xsmael Over a year ago

@patrick not at all, the OP asked how to run a another process without blocking; not how to keep the script running even after the user closes the connection

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