Add multi-listen example

examples/multi-listen.php

@@ -0,0 +1,63 @@
+#!/usr/bin/env php
+<?php
+
+require dirname(__DIR__) . '/vendor/autoload.php';
+
+use Amp\Iterator;
+use Amp\Loop;
+use Amp\Postgres;
+
+Loop::run(function () {
+    $pool = Postgres\pool('host=localhost user=postgres');
+
+    $channel1 = "test1";
+    $channel2 = "test2";
+
+    /** @var \Amp\Postgres\Listener $listener1 */
+    $listener1 = yield $pool->listen($channel1);
+
+    printf("Listening on channel '%s'\n", $listener1->getChannel());
+
+    /** @var \Amp\Postgres\Listener $listener2 */
+    $listener2 = yield $pool->listen($channel2);
+
+    printf("Listening on channel '%s'\n", $listener2->getChannel());
+
+    Loop::delay(6000, function () use ($listener1) { // Unlisten in 6 seconds.
+        printf("Unlistening from channel '%s'\n", $listener1->getChannel());
+        return $listener1->unlisten();
+    });
+
+    Loop::delay(4000, function () use ($listener2) { // Unlisten in 4 seconds.
+        printf("Unlistening from channel '%s'\n", $listener2->getChannel());
+        return $listener2->unlisten();
+    });
+
+    Loop::delay(1000, function () use ($pool, $channel1) {
+        return $pool->notify($channel1, "Data 1.1");
+    });
+
+    Loop::delay(2000, function () use ($pool, $channel2) {
+        return $pool->notify($channel2, "Data 2.1");
+    });
+
+    Loop::delay(3000, function () use ($pool, $channel2) {
+        return $pool->notify($channel2, "Data 2.2");
+    });
+
+    Loop::delay(5000, function () use ($pool, $channel1) {
+        return $pool->notify($channel1, "Data 1.2");
+    });
+
+    $iterator = Iterator\merge([$listener1, $listener2]); // Merge both listeners into single iterator.
+
+    while (yield $iterator->advance()) {
+        $notification = $iterator->getCurrent();
+        printf(
+            "Received notification from PID %d on channel '%s' with payload: %s\n",
+            $notification->pid,
+            $notification->channel,
+            $notification->payload
+        );
+    }
+});