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To make use of multiple cores for some rather long processing operations I needed a way to fork multiple workers from a single PHP script multiple times lately. So I created this small project which implements this in a way, so that it should reusable by anybody.

The implementation and usage is pretty simple. There is in an interface JobProvider which has the methods hasJobs() and getNextJob(), which you need to implement. The second method should return valid PHP callbacks - for example Closures. Those are then executed (in parallel) by the executor.

I also implemented a ShellJobProvider (which implements JobProvider), which is constructed from an array of shell commands, which then are executed in parallel. A simple working example:

<?php

require 'njq/environment.php';

$executor = new \njq\Executor();
$executor->run(
    new \njq\ShellJobProvider( array(
        'echo 1 >> test',
        'echo 2 >> test',
        'echo 3 >> test',
        'echo 4 >> test',
        'echo 5 >> test',
    ) ),
    4
);

?>

The file test will then contain something like (the order might vary):

5
4
3
2
1

The 4 (second parameter of \njq\Executor::run) defines the number of parallel processes to spawn. This should not exceed the number of available cores in the most cases.

To view the state of the executor you can specify a logger, which then can echo the current progress. A logger needs to implement the \njq\Logger interface and is passed to the constructor of the executor. If no logger is specified a blind dummy logger will be used. To use the shell logger, echoing the state to STDERR, use:

<?php

require 'njq/environment.php';

$executor = new \njq\Executor( new \njq\ShellLogger() );
$executor->run(
    new \njq\ShellJobProvider( array(
        // ...
    ) ),
    4
);

It will then print a status like the following, if the JobProvider implements the Countable interface:

56 / 5880 (0.95%) |

If the JobProvider does not implement the Countable interface the percent indicator obviously cannot be displayed.

The job queue requires PHP 5.3 and the PHP PCNTL extension.