Use GCR images from 'google-samples' project; allow switch on whether dns service is

supported, or to use env vars to get service host info.

Test change to reflect php filename change.

examples/guestbook/php-redis/guestbook.php

@@ -0,0 +1,43 @@
+<?
+
+set_include_path('.:/usr/local/lib/php');
+
+error_reporting(E_ALL);
+ini_set('display_errors', 1);
+
+require 'Predis/Autoloader.php';
+
+Predis\Autoloader::register();
+
+if (isset($_GET['cmd']) === true) {
+  $host = 'redis-master';
+  if (getenv('GET_HOSTS_FROM') == 'env') {
+    $host = getenv('REDIS_MASTER_SERVICE_HOST');
+  }
+  header('Content-Type: application/json');
+  if ($_GET['cmd'] == 'set') {
+    $client = new Predis\Client([
+      'scheme' => 'tcp',
+      'host'   => $host,
+      'port'   => 6379,
+    ]);
+
+    $client->set($_GET['key'], $_GET['value']);
+    print('{"message": "Updated"}');
+  } else {
+    $host = 'redis-slave';
+    if (getenv('GET_HOSTS_FROM') == 'env') {
+      $host = getenv('REDIS_SLAVE_SERVICE_HOST');
+    }
+    $client = new Predis\Client([
+      'scheme' => 'tcp',
+      'host'   => $host,
+      'port'   => 6379,
+    ]);
+
+    $value = $client->get($_GET['key']);
+    print('{"data": "' . $value . '"}');
+  }
+} else {
+  phpinfo();
+} ?>