how to use php exec(), to run another script and run in the backround, and not wait for the script to finish

Question

I am wanting to execute a large, database intensive script, but do not need to wait for the process to finish. I would simply like to call the script, let it run in the background and then redirect to another page.

EDIT: i am working on a local Zend community server, on Windows 7. I have access to remote linux servers where the project also resides, so i can do this on linux or windows.

i have this

public function createInstanceAction()
{
    //calls a seperate php process which creates the instance
    exec('php -f /path/to/file/createInstance.php');


    Mage::getSingleton('adminhtml/session')->addSuccess(Mage::helper('adminhtml')->__('Instance creation process started. This may take up to a few minutes.'));
    $this->_redirect('instances/adminhtml_instances/');
    return;
}

this works perfectly, but the magento application hangs around for the process to finish. it does everything i expect, logging to file from time to time, and am happy with how its running. Now all i would like to do is have this script start, the controller action does not hang around, but instead redirects and thats that. from what I have learnt about exec(), you can do so by changing the way i call exec() above, to :

exec('php -f /path/to/file/createInstance.php > /dev/null 2>&1 &');

which i took from here

if i add "> /dev/null 2>&1 &" to the exec call, it doesnt wait around as expected, but it does not execute the script anymore. Could someone tell me why, and if so, tell me how i can get this to work please?

Could this be a permission related issue?

thanks

EDIT : Im assuming it would be an issue to have any output logged to file if i call the exec function with (/dev/null 2>&1 &) as that would cancel that. is that correct?

Answer 1

The PHP executable included with Zend Server seems to be what's causing attempts to run a script in the background (using the ampersand & operator in the exec) to fail.

We tested this using our standard PHP executable and it worked fine. It's something to do with the version shipped with Zend Server though our limited attempts to figure out what that was going on have not turned anything up.

Answer 2

After taking time to fully understand my own question and the way it could be answered, i have prepared my solution.

Thanks to all for your suggestions, and for excusing my casual, unpreparedness when asking the question.

The answer to the above question depends on a number of things, such as the operating system you are referring to, which php modules you are running and even as far as what webserver you are running. So if i had to start the question again, the first thing i would do is state what my setup is.

I wanted to achieve this on two environments :

1.) Windows 7 running Zend server community edition. 2.) Linux (my OS is Linux odysseus 2.6.32-5-xen-amd64 #1 SMP Fri Sep 9 22:23:19 UTC 2011 x86_64)

to get this right, i wanted it to work either way when deploying to windows or linux, so i used php to determine what the operating system was.

public function createInstanceAction()
{

    //determines what operating system is Being used 
    if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN')
    {
        //This is a windows server

        //call a seperate php process to run independently from the broswer action

        pclose(popen("start php /path/to/script/script.php","r"));

    }
    else
    {
        //assuming its linux, but in fact it simply means its not windows
        // to check for linux specifically use (strtoupper(substr(PHP_OS, 0, 3)) === 'LIN')
        exec('php -f /path/to/file/script.php >/dev/null 2>&1 &');
    }
    //the browser will not hang around for this process to complete, and you can contimue with whatever actions you want.

    //myscript log any out put so i can capture info as it runs
}

In short, ask questions once you understand them. there are many ways to to achieve the above, and this is just one solution that works for my development and production environments.

thanks for the help all.

Answer 3

I've been able to use:

shell_exec("nohup $command  > /dev/null & echo $!")

Where $command is for example:

php script.php --parameter 1

I've noticed some strange behavior with this. For example running mysql command line doesn't work, only php scripts seem to work.

Also, running cd /path/to/dir && php nohup $command ... doesn't work either, I had to chdir() within the PHP script and then run the command for it to work.

Answer 4

You could write a wrapper-script, say createInstance.sh like

#! /bin/bash

trap "" SIGHUP
php -f "$1" > logfile.txt 2>&1 &

Then you call the script from within PHP:

exec('bash "/path/to/file/createInstance.sh"');

which should detach the new php process most instantly from the script. If that doesen't help, you might try to use SIGABRT, SIGTERM or SIGINT instead of SIGHUP, I don't know exactly which signal is sent.

Answer 5

PHP popen

From the docs (this should help you do other stuff, while that process is working; not sure if closing the current PHP process will kill the opened process):

/* Add redirection so we can get stderr. */
$handle = popen('/path/to/executable 2>&1', 'r');
echo "'$handle'; " . gettype($handle) . "\n";
$read = fread($handle, 2096);
echo $read;
pclose($handle);

Solution 2: Trick the browser to close the connection (assuming there is a browser involved):

ob_start();
?><html><!--example html body--></html><?php
$strContents=ob_get_clean(); 

header("Connection: Close");
header("Content-encoding: none");//doesn't work without this, I don't know why:(

ignore_user_abort(true);

header("Content-type: text/html");
header("Content-Length: ".strlen($strContents));
echo $strContents;

flush();
//at this point a real browser would close the connection and finish rendering; 
//crappy http clients like some curl implementations (and not only) would wait for the server to close the connection, then finish rendering/serving results...:(

//TODO: add long running operations here, exec, or whatever you have.