Merge pull request #1 from LearningLocker/issue/uuid-variant

Fixes variant checking.

Author: ryasmi

src/RegexpAtom.php

@@ -7,7 +7,7 @@ class RegexpAtom extends Atom {
   protected static $invalid_message;
 
   protected function getInvalidMessage() {
-    return static::$invalid_message ?: '`'.$this->value.'` should be a valid `' . get_class($this) . '`';
+    return static::$invalid_message .'`'.$this->value.'` should be a valid `' . get_class($this) . '`';
   }
 
   public function validate() {

src/UUID.php

@@ -1,5 +1,6 @@
 <?php namespace Locker\XApi;
 
 class UUID extends RegexpAtom {
-  protected static $pattern = '/^\{?[A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{12}\}?$/i';
+  protected static $pattern = '/^\{?[A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[8,9,a,b][A-Z0-9]{3}-[A-Z0-9]{12}\}?$/i';
+  protected static $invalid_message = 'Only versions of variant 2 in RFC 4122 are valid. ';
 }