refactored State pattern example

Behavioral/State/StateShipped.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace DesignPatterns\Behavioral\State;
+
+class StateShipped implements State
+{
+    public function proceedToNext(OrderContext $context)
+    {
+        $context->setState(new StateDone());
+    }
+
+    public function toString(): string
+    {
+        return 'shipped';
+    }
+}