diff --git a/Singleton/Singleton.php b/Singleton/Singleton.php
index ee896e4..c728c31 100644
--- a/Singleton/Singleton.php
+++ b/Singleton/Singleton.php
@@ -16,6 +16,11 @@ namespace DesignPatterns;
  */
 class Singleton
 {
+    /**
+     * @var cached reference to singleton instance 
+     */
+    protected static $instance;
+    
     /**
      * gets the instance via lazy initialization (created on first usage)
      *
@@ -23,13 +28,12 @@ class Singleton
      */
     public static function getInstance()
     {
-        static $instance;
-
-        if (null === $instance) {
-            $instance = new self();
+        
+        if (null === static::$instance) {
+            static::$instance = new static;
         }
 
-        return $instance;
+        return static::$instance;
     }
 
     /**