deferred.php

<?php

require_once './vendor/autoload.php';

abstract class Element
{
	protected $loop;
	public $active = false;

	public function __construct(\React\EventLoop\LoopInterface $loop)
	{
		$this->loop = $loop;
	}

	abstract public function synchronize();
}

class A extends Element
{

	public function synchronize()
	{
		$deferred = new \React\Promise\Deferred();

		echo 'Processing A ...'.PHP_EOL;
		$i = 7;
		$this->loop->addPeriodicTimer(0.5, function ($time) use (&$i, $deferred) {
			echo date('H:i:s').'| $A: '.$i.PHP_EOL;
			sleep(1);
			$i--;
			if ($i <= 0) {
				$time->cancel();
				$deferred->resolve();
				echo 'Finished processing A ...'.PHP_EOL;

			}
		});

		return $deferred->promise();
	}
}

class B extends Element
{
	public function synchronize()
	{
		$deferred = new \React\Promise\Deferred();

		echo 'Processing B ...'.PHP_EOL;
		$i = 5;
		$this->loop->addPeriodicTimer(0.5, function ($time) use (&$i, $deferred) {
			echo date('H:i:s').'| $B: '.$i.PHP_EOL;
			sleep(1);
			$i--;
			if ($i <= 0) {
				$time->cancel();
				$deferred->resolve();
				echo 'Finished processing B ...'.PHP_EOL;
			}
		});

		return $deferred->promise();
	}
}

class Test
{
	protected $loop;
	public $deferred;
	public $a;
	public $b;

	public function __construct()
	{
		$this->loop = React\EventLoop\Factory::create();
		$this->deferred = new \React\Promise\Deferred();
		$this->promise = $this->deferred->promise();

		$this->a = new A($this->loop);
		$this->b = new B($this->loop);
	}

	public function run()
	{
		$that = $this;

		$this->loop->addPeriodicTimer(1, function () {
			echo '.'.PHP_EOL;
		});

		$this->loop->addTimer(5, function () use ($that) {
			echo 'run a'.PHP_EOL;
			$that->deferred = $that->deferred->then($that->a->synchronize());
		});
		$this->loop->addTimer(3, function () use ($that) {
			echo 'run b'.PHP_EOL;
			$that->deferred = $that->deferred->then($that->b->synchronize());
		});

		$this->loop->addTimer(6, function () use ($that) {
			echo 'run b once more'.PHP_EOL;
			$that->deferred = $that->deferred->then($that->b->synchronize());
		});

		$this->loop->run();
	}


}

$test = new Test();
$test->run();

output.txt

.
.
run b
Processing B ...
.
14:11:31| $B: 5
.
14:11:33| $B: 4
run a
Processing A ...
14:11:34| $B: 3
14:11:35| $A: 7
run b once more
Processing B ...
.
14:11:37| $B: 2
14:11:38| $B: 5
14:11:39| $A: 6
.
14:11:40| $B: 1
Finished processing B ...
14:11:41| $A: 5
14:11:42| $B: 4
.
14:11:44| $A: 4
14:11:45| $B: 3
.
14:11:46| $A: 3
14:11:47| $B: 2
.
14:11:49| $A: 2
14:11:50| $B: 1
Finished processing B ...
.
14:11:51| $A: 1
Finished processing A ...
.
.