Fix conflicting index bug

Author: Hassan Almas

jsonld.php

@@ -3695,7 +3695,9 @@ protected function _createNodeMap(
 
       // copy non-@type keywords
       if($property !== '@type' && self::_isKeyword($property)) {
-        if($property === '@index' && property_exists($subject, '@index')) {
+        if($property === '@index' && property_exists($subject, '@index')
+        && ($input->{'@index'} !== $subject->{'@index'}
+           || $input->{'@index'}->{'@id'} !== $subject->{'@index'}->{'@id'})) {
           throw new JsonLdException(
             'Invalid JSON-LD syntax; conflicting @index property detected.',
             'jsonld.SyntaxError', 'conflicting indexes',