start a restructure

Behavioral/Mediator/Colleague.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace DesignPatterns\Mediator;
+
+/**
+ * Colleague is an abstract colleague who works together but he only knows
+ * the Mediator, not other colleague.
+ */
+abstract class Colleague
+{
+    /**
+     * this ensures no change in subclasses
+     *
+     * @var MediatorInterface
+     */
+    private $mediator;
+
+    // for subclasses
+    protected function getMediator()
+    {
+        return $this->mediator;
+    }
+
+    /**
+     * @param MediatorInterface $medium
+     */
+    public function __construct(MediatorInterface $medium)
+    {
+        // in this way, we are sure the concrete colleague knows the mediator
+        $this->mediator = $medium;
+    }
+}