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msd2/tracking/piwik/core/Singleton.php

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+<?php
+/**
+ * Piwik - free/libre analytics platform
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ *
+ */
+
+namespace Piwik;
+
+/**
+ * The singleton base class restricts the instantiation of derived classes to one object only.
+ *
+ * All plugin APIs are singletons and thus extend this class.
+ *
+ * @api
+ */
+class Singleton
+{
+    protected static $instances;
+
+    protected function __construct()
+    {
+    }
+
+    final private function __clone()
+    {
+    }
+
+    /**
+     * Returns the singleton instance for the derived class. If the singleton instance
+     * has not been created, this method will create it.
+     *
+     * @return static
+     */
+    public static function getInstance()
+    {
+        $class = get_called_class();
+
+        if (!isset(self::$instances[$class])) {
+            self::$instances[$class] = new $class;
+        }
+        return self::$instances[$class];
+    }
+
+    /**
+     * Used in tests only
+     * @ignore
+     */
+    public static function unsetInstance()
+    {
+        $class = get_called_class();
+        unset(self::$instances[$class]);
+    }
+
+    /**
+     * Sets the singleton instance. For testing purposes.
+     * @ignore
+     */
+    public static function setSingletonInstance($instance)
+    {
+        $class = get_called_class();
+        self::$instances[$class] = $instance;
+    }
+
+    /**
+     * @ignore
+     */
+    public static function clearAll()
+    {
+        self::$instances = array();
+    }
+}