Added Service Locator pattern

ServiceLocator/ServiceLocatorInterface.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+interface ServiceLocatorInterface 
+{
+    /**
+     * Checks if a service is registered.
+     *
+     * @param string $interface
+     *
+     * @return bool
+     */
+    public function has($interface);
+
+    /**
+     * Gets the service registered for the interface.
+     *
+     * @param string $interface
+     *
+     * @return mixed
+     */
+    public function get($interface);
+}