Add polyfill for \JsonSerializable

Author: glensc

composer.json

@@ -29,6 +29,7 @@
         "sort-packages": true
     },
     "autoload": {
+        "files": [ "src/polyfill.php" ],
         "classmap": [
             "./"
         ]

src/polyfill.php

@@ -0,0 +1,15 @@
+<?php
+
+/**
+ * Polyfill for PHP < 5.4
+ */
+if (!interface_exists('JsonSerializable', false)) {
+    interface JsonSerializable
+    {
+        /**
+         * @param void
+         * @return mixed
+         */
+        function jsonSerialize();
+    }
+}