added Command pattern

Command/Command.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace DesignPatterns;
+
+/**
+ * Command pattern
+ *
+ * Purpose:
+ * to build a simple interface for commands that can all be run by just executing a single method they all have in
+ * common, often called 'run' or 'execute'
+ *
+ * Examples:
+ * - Symfony2: SF2 Commands that can be run from the CLI are built with just the Command pattern in mind
+ * - big CLI tools use subcommands to distribute various tasks and pack them in "modules", each of these
+ *   can be implemented with the Command pattern (e.g. vagrant)
+ *
+ */
+interface CommandInterface
+{
+    /**
+     * this is the most important method in the Command pattern,
+     * all config options and parameters should go into the constructor
+     *
+     * @return mixed
+     */
+    public function execute();
+}
+
+class EchoCommand implements CommandInterface
+{
+    public function __construct($what)
+    {
+        $this->what = (string)$what;
+    }
+
+    public function execute()
+    {
+        echo $this->what;
+    }
+}