diff --git a/lib/php/Collections.php b/lib/php/Collections.php
index f98ebb8..3ec608d 100644
--- a/lib/php/Collections.php
+++ b/lib/php/Collections.php
@@ -193,7 +193,7 @@ public function fetchCollections($params = array()){
         }
         
         $feed = new Zotero_Feed($response->getRawBody());
-        $this->owningLibrary->_lastFeed = $feed;
+        $this->owningLibrary->setLastFeed($feed);
         $addedCollections = $this->addCollectionsFromFeed($feed);
         
         if(isset($feed->links['next'])){
diff --git a/lib/php/Library.php b/lib/php/Library.php
index 18ce4a3..3013a5c 100644
--- a/lib/php/Library.php
+++ b/lib/php/Library.php
@@ -54,6 +54,14 @@ public function __construct($libraryType = null, $libraryID = null, $libraryUrlI
         if (!extension_loaded('curl')) {
             throw new Exception("You need cURL");
         }
+        //check if APC is loaded
+        if (!extension_loaded('apc') && !ini_get('apc.enabled')) {
+            throw new Exception("PHP extension APC is not loaded/or enabled in php.ini");
+        }
+        //check if DOMDocument object is loaded
+        if (!extension_loaded('xml')) {
+            throw new Exception("PHP extension XML is not loaded");
+        }
         
         $this->libraryType = $libraryType;
         $this->libraryID = $libraryID;
@@ -271,6 +279,16 @@ public function getLastFeed(){
         return $this->_lastFeed;
     }
     
+    /**
+     *  Sets the last Zotero_Feed
+     *
+     * @param Zotero_feed
+     */
+    public function setLastFeed($feed)
+    {
+        $this->_lastFeed = $feed;
+    }
+
     /**
      * Construct a string that uniquely identifies a library
      * This is not related to the server GUIDs