start a restructure

Behavioral/NullObject/NullLogger.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace DesignPatterns\NullObject;
+
+/**
+ * Performance concerns : ok there is a call for nothing but we spare an "if is_null"
+ * I didn't run a benchmark but I think it's equivalent.
+ * 
+ * Key feature : of course this logger MUST implement the same interface (or abstract)
+ * like the other loggers.
+ */
+class NullLogger implements LoggerInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function log($str)
+    {
+        // do nothing
+    }
+}