kriswallsmith/spork

<?php

$manager = new Spork\ProcessManager();
$manager->fork(function() {
    // do something in another process!
    return 'Hello from '.getmypid();
})->then(function(Spork\Fork $fork) {
    // do something in the parent process when it's done!
    echo "{$fork->getPid()} says '{$fork->getResult()}'\n";
});

<?php

$files = new RecursiveDirectoryIterator('/path/to/images');
$files = new RecursiveIteratorIterator($files);

$manager->process($files, function(SplFileInfo $file) {
    // upload this file
});