Add utility class to Base64 en/decode in a URL safe fashion.

Author: Potherca

src/Utils/Base64Url.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Pdsinterop\Solid\Auth\Utils;
+
+/**
+ * URL-safe Base64 encode and decode
+ *
+ * ...as PHP does not natively offer this functionality
+ */
+class Base64Url
+{
+    private const URL_UNSAFE = '+/';
+    private const URL_SAFE = '-_';
+
+    public static function encode($subject) : string
+    {
+        return strtr(rtrim(base64_encode($subject), '='), self::URL_UNSAFE, self::URL_SAFE);
+    }
+
+    public static function decode($subject) : string
+    {
+        return base64_decode(strtr($subject, self::URL_SAFE, self::URL_UNSAFE));
+    }
+}