On live cluster, Language::isValidBuiltInCode is being passed an object when the method expect a string (which is then passed to preg_match).
May 16 13:52:33 10.0.2.195 apache2[30042]: PHP Warning: preg_match() expects parameter 2 to be string, object given in /usr/local/apache/common-local/php-1.20wmf2/languages/Language.php on line 248
Version: 1.20.x
Severity: normal