added Singleton

Dominik Liebler · Dominik Liebler · commit e730ee6e8eca · 2011-08-21T15:36:40.000+02:00
diff --git a/Singleton/Singleton.php b/Singleton/Singleton.php
@@ -0,0 +1,68 @@
+<?php
+/**
+ * Created by JetBrains PhpStorm.
+ * User: dominik
+ * Date: 21.08.11
+ * Time: 15:16
+ * To change this template use File | Settings | File Templates.
+ */
+
+namespace DesignPatterns;
+
+/**
+ * Singleton pattern
+ *
+ * Purpose:
+ *  - to have only one instance of this object in the application, that handles all calls
+ *
+ * Examples:
+ * - DB Connector
+ * - Logger (May also be a Multiton if there are many Logfiles for several purposes)
+ * - Lock file for the application (there is only one in the filesystem ...)
+ *
+ *
+ */
+class Singleton
+{
+    /**
+     * @var \DesignPatterns\Singleton
+     */
+    private static $_instance;
+
+    /**
+     * gets the instance via lazy initialization (created on first usage)
+     *
+     * @return Singleton
+     */
+    public function getInstance()
+    {
+        if (null === self::$_instance) {
+            self::$_instance = new self();
+        }
+
+        return self::$_instance;
+    }
+
+    /**
+     * is not allowed to call from outside: private!
+     *
+     */
+    private function __construct()
+    {}
+
+    /**
+     * prevent the instance from being cloned
+     *
+     * @return void
+     */
+    private function __clone()
+    {}
+
+    /**
+     * prevent from being unserialized
+     *
+     * @return void
+     */
+    private function __wakeup()
+    {}
+}
