Made the code more robust.

Extended functionality with helper functions.

bin/app.php

@@ -3,33 +3,42 @@
 
 require_once __DIR__ . '/../vendor/autoload.php';
 
+use function Joop\Asynchronous\async;
+use Joop\Asynchronous\Promise;
 
-// Create a function we want to run asynchronously
-$process = function ($i) {
-	$delayMicroseconds = (10 - $i) * 1000000;
-	usleep($delayMicroseconds);
-
-	return getmypid();
-};
-
-
-// Execute the functions asynchronously - each returning a Promise
-$promises = [];
-foreach (range(0, 10) as $i)
-	$promises[] = Asynchronous::run($process, $i);
-
-
-// Wait for all promises to resolve
-while (count($promises) > 0) {
+/**
+ * @param Promise[] $promises
+ */
+function awaitPromises(array &$promises)
+{
 	foreach ($promises as $index => $promise) {
-		if ($promise->isResolved() && !$promise->isEmpty()) {
-			print("Response retrieved: " . $promise->getValue() . PHP_EOL);
+		if ($promise->isResolved()) {
 			unset($promises[$index]);
+
+			if (!$promise->isEmpty() && !$promise->isError())
+				print($promise->getValue() . PHP_EOL);
 		}
 	}
 }
 
 
-exit(0);
+/*
+ * Example of asynchronous processing in PHP
+ */
 
+$process = function ($i) {
+	$delayMicroseconds = (5 - $i) * 1000000;
+	usleep($delayMicroseconds);
 
+	return sprintf(
+		'PID %-5d slept for %.1f seconds',
+		getmypid(), $delayMicroseconds / 1000000
+	);
+};
+
+$promises = [];
+foreach (range(0, 5) as $i)
+	$promises[] = async($process, $i);
+
+while (count($promises) > 0)
+	awaitPromises($promises);