add piwik installation

www/analytics/core/View/ViewInterface.php

@@ -0,0 +1,25 @@
+<?php
+/**
+ * Piwik - Open source web analytics
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ *
+ */
+
+namespace Piwik\View;
+
+/**
+ * Rendering interface for all "view" types.
+ *
+ * @api
+ */
+interface ViewInterface
+{
+    /**
+     * Returns data.
+     *
+     * @return string Serialized data, eg, (image, array, html...).
+     */
+    function render();
+}