some explanations

Observer/UserObserver.php

@@ -18,6 +18,12 @@ namespace DesignPatterns\Observer;
 class UserObserver implements \SplObserver
 {
 
+    /**
+     * This is the only method to implement as an observer.
+     * It is called by the Subject (usually by SplSubject::notify() )
+     * 
+     * @param \SplSubject $subject
+     */
     public function update(\SplSubject $subject)
     {
         echo get_class($subject) . ' has been updated';