Aerys\WatcherProcess::spawn PHP Method

    private function spawn()
    {
        $cmd = $this->workerCommand;
        $fds = [["pipe", "r"], ["pipe", "w"], ["pipe", "w"]];
        $options = ["bypass_shell" => true];
        if (!($procHandle = \proc_open($cmd, $fds, $pipes, null, null, $options))) {
            return new Failure(new \RuntimeException("Failed spawning worker process"));
        }
        foreach ($pipes as $pipe) {
            @fclose($pipe);
        }
        $this->processes[] = $procHandle;
        return ($this->spawnPromisors[] = new Deferred())->promise();
    }