Move Redis collections iterators in a different namespace.

The base iterator class is now known as RedisCollectionIterator and
we've also renamed a few methods to make their naming more generic.

examples/RedisCollectionsIterators.php

@@ -0,0 +1,99 @@
+<?php
+
+/*
+ * This file is part of the Predis package.
+ *
+ * (c) Daniele Alessandri <suppakilla@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+require 'SharedConfigurations.php';
+
+use Predis\Collection\Iterator\KeyspaceIterator;
+use Predis\Collection\Iterator\SetIterator;
+use Predis\Collection\Iterator\SortedSetIterator;
+use Predis\Collection\Iterator\HashIterator;
+
+// Redis 2.8 features new commands allowing clients to incrementally
+// iterate over collections without blocking the server like it happens
+// when a command such as KEYS is executed on a Redis instance storing
+// millions of keys. These commands are SCAN (iterates over the keyspace),
+// SSCAN (iterates over members of a set), ZSCAN (iterates over members
+// and ranks of a sorted set) and HSCAN (iterates over fields and values
+// of an hash). Predis provides a specialized abstraction for each command
+// based on SPL iterators making it possible to easily consume SCAN-based
+// iterations in your PHP code.
+//
+// See http://redis.io/commands/scan for more details.
+//
+
+// Create a client using `2.8` as a server profile (needs Redis 2.8!)
+$client = new Predis\Client($single_server, array('profile' => '2.8'));
+
+// Prepare some keys for our example
+$client->del('predis:set', 'predis:zset', 'predis:hash');
+for ($i = 0; $i < 5; $i++) {
+    $client->sadd('predis:set', "member:$i");
+    $client->zadd('predis:zset', -$i, "member:$i");
+    $client->hset('predis:hash', "field:$i", "value:$i");
+}
+
+// === KeyspaceIterator based on SCAN ===
+echo 'Scan the keyspace matching only our prefixed keys:' . PHP_EOL;
+foreach (new KeyspaceIterator($client, 'predis:*') as $key) {
+    echo " - $key" . PHP_EOL;
+}
+
+/* OUTPUT
+Scan the keyspace matching only our prefixed keys:
+ - predis:zset
+ - predis:set
+ - predis:hash
+*/
+
+// === SetIterator class based on SSCAN ===
+echo 'Scan members of `predis:set`:' . PHP_EOL;
+foreach (new SetIterator($client, 'predis:set') as $member) {
+    echo " - $member" . PHP_EOL;
+}
+
+/* OUTPUT
+Scan members of `predis:set`:
+ - member:1
+ - member:4
+ - member:0
+ - member:3
+ - member:2
+*/
+
+// === SortedSetIterator class based on ZSCAN ===
+echo 'Scan members and ranks of `predis:zset`:' . PHP_EOL;
+foreach (new SortedSetIterator($client, 'predis:zset') as $member => $rank) {
+    echo " - $member [rank: $rank]" . PHP_EOL;
+}
+
+/* OUTPUT
+Scan members and ranks of `predis:zset`:
+ - member:4 [rank: -4]
+ - member:3 [rank: -3]
+ - member:2 [rank: -2]
+ - member:1 [rank: -1]
+ - member:0 [rank: 0]
+*/
+
+// === HashIterator class based on HSCAN ===
+echo 'Scan fields and values of `predis:hash`:' . PHP_EOL;
+foreach (new HashIterator($client, 'predis:hash') as $field => $value) {
+    echo " - $field => $value" . PHP_EOL;
+}
+
+/* OUTPUT
+Scan fields and values of `predis:hash`:
+ - field:0 => value:0
+ - field:1 => value:1
+ - field:2 => value:2
+ - field:3 => value:3
+ - field:4 => value:4
+*/