diff --git a/modules/php/php.module b/modules/php/php.module
index 37bf9a1..0dd5af7 100644
--- a/modules/php/php.module
+++ b/modules/php/php.module
@@ -46,6 +46,9 @@ function php_permission() {
  * Using this wrapper also ensures that the PHP code which is evaluated can not
  * overwrite any variables in the calling code, unlike a regular eval() call.
  *
+ * This function is also used as an implementation of
+ * hook_filter_FILTER_process().
+ *
  * @param $code
  *   The code to evaluate.
  * @return