MDL-65217 form: option to randomise element ids

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.
      */

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);