diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 59570bffeea..cf784f50947 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -470,6 +470,7 @@ function GETPOSTISARRAY($paramname, $method = 0)
  *                               'alphanohtml'=check there is no html content and no " and no ../
  *                               'aZ'=check it's a-z only
  *                               'aZ09'=check it's simple alpha string (recommended for keys)
+ *                               'aZ09comma'=check it's a string for a sortfield or sortorder
  *                               'san_alpha'=Use filter_var with FILTER_SANITIZE_STRING (do not use this for free text string)
  *                               'nohtml'=check there is no html content and no " and no ../
  *                               'restricthtml'=check html content is restricted to some tags only