Base class for doing forked, parallel execution in PHP easily

ParallelTask.php

<?php
class ParallelTask
{
	protected $pid = null;

	public $max_workers = 8;

	protected $num_workers = 0;

	public function run()
	{
		$items = $this->get_data();
		foreach ($items as $item) {
			while ($this->num_workers < $this->max_workers) {
				$pid = pcntl_fork();

				// Error
				if ($pid == -1) {
					die('could not fork');
				}
				// Worker
				elseif ($pid === 0) {
					if ($this->do_work($item)) {
						exit(0);
					}
					else {
						exit(1);
					}
				}
				// Parent
				else {
					$this->num_workers++;
				}
			}
			// Wait until a child exits before trying to do more work
			pcntl_wait($status); //Protect against Zombie children
			$this->num_workers--;
		}
	}

	protected function do_work($id)
	{
		return true;
	}

	protected function get_data()
	{
		return array();
	}
}