init commit

plugins/xframework/common/Singleton.php

@@ -0,0 +1,36 @@
+<?php
+namespace XFramework;
+
+/**
+ * Roundcube Plus Framework plugin.
+ *
+ * Copyright 2016, Tecorama LLC.
+ *
+ * @license Commercial. See the LICENSE file for details.
+ * @codeCoverageIgnore
+ */
+
+trait Singleton {
+    protected static $instance;
+
+    public static function instance($parameters = null)
+    {
+        return static::$instance ?? static::$instance = new static($parameters);
+    }
+
+    public static function hasInstance(): bool
+    {
+        return (bool)static::$instance;
+    }
+
+    public static function deleteInstance()
+    {
+        if (static::hasInstance()) {
+            static::$instance = null;
+        }
+    }
+
+    final public function __clone() {} // restrict cloning
+    final public function __sleep() {} // restrict serializing
+    final public function __wakeup() {} // restrict unserializing
+}