From b02590628118b847412c1fe4c9827a9091844aed Mon Sep 17 00:00:00 2001
From: Dominik Liebler <dominik@liebler-web.de>
Date: Sat, 27 Aug 2011 10:34:12 +0200
Subject: [PATCH] added observer pattern

---
 Observer/Observer.php | 71 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 Observer/Observer.php

diff --git a/Observer/Observer.php b/Observer/Observer.php
new file mode 100644
index 0000000..5b7aacd
--- /dev/null
+++ b/Observer/Observer.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace DesignPatterns;
+
+/**
+ * Observer pattern
+ *
+ * Purpose:
+ * to implement a publish/subscribe behaviour to an object, whenever a "Subject" object changes it's state, the attached
+ * "Observers" will be notified. It is used to shorten the amount of coupled objects and uses loose coupling instead
+ *
+ * Examples:
+ * - a message queue system is observed to show the progress of a job in a GUI
+ *
+ * PHP already defines two interfaces that can help to implement this pattern: SplObserver and SplSubject
+ *
+ */
+class UserObserver implements \SplObserver
+{
+    public function update(\SplSubject $subject)
+    {
+        echo get_class($subject) . ' has been updated';
+    }
+}
+
+class User implements \SplSubject
+{
+    /**
+     * @var array
+     */
+    protected $_observers = array();
+
+    /**
+     * attach a new observer
+     *
+     * @param \SplObserver $observer
+     * @return void
+     */
+    public function attach(\SplObserver $observer)
+    {
+        $this->_observers[] = $observer;
+    }
+
+    /**
+     * detach an observer
+     *
+     * @param \SplObserver $observer
+     * @return void
+     */
+    public function detach(\SplObserver $observer)
+    {
+        $index = array_search($observer, $this->_observers);
+
+        if (false !== $index) {
+            unset($this->_observers[$index]);
+        }
+    }
+
+    /**
+     * 
+     *
+     * @return void
+     */
+    public function notify()
+    {
+        /** @var SplObserver $observer */
+        foreach ($this->_observers as $observer) {
+            $observer->update($this);
+        }
+    }
+}
\ No newline at end of file