start a restructure

Behavioral/Visitor/RoleVisitorInterface.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace DesignPatterns\Visitor;
+
+/**
+ * Visitor Pattern
+ *
+ * The contract for the visitor.
+ * 
+ * Note 1 : in C++ or java, with method polymorphism based on type-hint, there are many
+ * methods visit() with different type for the 'role' parameter.
+ * 
+ * Note 2 : the visitor must not choose itself which method to
+ * invoke, it is the Visitee that make this decision.
+ */
+interface RoleVisitorInterface
+{
+    /**
+     * Visit a User object
+     * 
+     * @param \DesignPatterns\Visitor\User $role
+     */
+    public function visitUser(User $role);
+
+    /**
+     * Visit a Group object
+     * 
+     * @param \DesignPatterns\Visitor\Group $role
+     */
+    public function visitGroup(Group $role);
+}