Added fetchAllKeys example as per #494

Author: Geolim4

docs/examples/fetchAllKeys.php

@@ -0,0 +1,56 @@
+<?php
+/**
+ *
+ * This file is part of phpFastCache.
+ *
+ * @license MIT License (MIT)
+ *
+ * For full copyright and license information, please see the docs/CREDITS.txt file.
+ *
+ * @author Khoa Bui (khoaofgod)  <[email protected]> http://www.phpfastcache.com
+ * @author Georges.L (Geolim4)  <[email protected]>
+ *
+ */
+use phpFastCache\CacheManager;
+
+// Include composer autoloader
+require __DIR__ . '/../../vendor/autoload.php';
+
+$InstanceCache = CacheManager::getInstance('files');
+$InstanceCache->clear();
+
+/**
+ * @var $keys \phpFastCache\Core\Item\ExtendedCacheItemInterface[]
+ */
+$keyPrefix = "product_page_";
+$keys = [];
+
+for ($i=1;$i<=10;$i++)
+{
+    $keys[$keyPrefix . $i] = $InstanceCache->getItem($keyPrefix . $i);
+    if(!$keys[$keyPrefix . $i]->isHit()){
+        $keys[$keyPrefix . $i]
+          ->set(uniqid('pfc', true))
+          ->addTag('pfc');
+    }
+}
+
+$InstanceCache->saveMultiple($keys);
+
+/**
+ * Remove items references from memory
+ */
+unset($keys);
+$InstanceCache->detachAllItems();
+gc_collect_cycles();
+
+
+/**
+ * Now get the items by a specific tag
+ */
+$keys = $InstanceCache->getItemsByTag('pfc');
+foreach ($keys as $key) {
+    echo "Key: {$key->getKey()} =&gt; {$key->get()}<br />";
+}
+
+echo '<br /><br /><a href="/">Back to index</a>&nbsp;--&nbsp;<a href="./' . basename(__FILE__) . '">Reload</a>';