From f82c9d8d061e1c3874bb12a5fee8dfd84e69493a Mon Sep 17 00:00:00 2001
From: Marina Glancy <marina@moodle.com>
Date: Tue, 9 Apr 2019 15:40:52 +0200
Subject: [PATCH] MDL-65217 form: option to randomise element ids

---
 lib/formslib.php                    | 2 ++
 lib/pear/HTML/QuickForm/element.php | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/lib/formslib.php b/lib/formslib.php
index 9e2c96f0190..18fe4710420 100644
--- a/lib/formslib.php
+++ b/lib/formslib.php
@@ -163,6 +163,8 @@ abstract class moodleform {
      * @param string $target target frame for form submission. You will rarely use this. Don't use
      *               it if you don't need to as the target attribute is deprecated in xhtml strict.
      * @param mixed $attributes you can pass a string of html attributes here or an array.
+     *               Special attribute 'data-random-ids' will randomise generated elements ids. This
+     *               is necessary when there are several forms on the same page.
      * @param bool $editable
      * @param array $ajaxformdata Forms submitted via ajax, must pass their data here, instead of relying on _GET and _POST.
      */
diff --git a/lib/pear/HTML/QuickForm/element.php b/lib/pear/HTML/QuickForm/element.php
index 18332ea9997..042f1910d63 100644
--- a/lib/pear/HTML/QuickForm/element.php
+++ b/lib/pear/HTML/QuickForm/element.php
@@ -384,6 +384,10 @@ class HTML_QuickForm_element extends HTML_Common
         switch ($event) {
             case 'createElement':
                 static::__construct($arg[0], $arg[1], $arg[2], $arg[3], $arg[4]);
+                if ($caller->getAttribute('data-random-ids') && !$this->getAttribute('id')) {
+                    $this->_generateId();
+                    $this->updateAttributes(array('id' => $this->getAttribute('id') . '_' . random_string()));
+                }
                 break;
             case 'addElement':
                 $this->onQuickFormEvent('createElement', $arg, $caller);