parent::__construct('langlist', get_string('langlist', 'admin'), get_string('configlanglist', 'admin'), '', PARAM_NOTAGS);
}
+ /**
+ * Validate that each language identifier exists on the site
+ *
+ * @param string $data
+ * @return bool|string True if validation successful, otherwise error string
+ */
+ public function validate($data) {
+ $parentcheck = parent::validate($data);
+ if ($parentcheck !== true) {
+ return $parentcheck;
+ }
+
+ if ($data === '') {
+ return true;
+ }
+
+ // Normalize language identifiers.
+ $langcodes = array_map('trim', explode(',', $data));
+ foreach ($langcodes as $langcode) {
+ // If the langcode contains optional alias, split it out.
+ [$langcode, ] = preg_split('/\s*\|\s*/', $langcode, 2);
+
+ if (!get_string_manager()->translation_exists($langcode)) {
+ return get_string('invalidlanguagecode', 'error', $langcode);
+ }
+ }
+
+ return true;
+ }
+
/**
* Save the new setting
*
