Thread:Project:Support desk/ERROR from CategoryTree Extension/reply (3)

Is there a reason you're using such an old version of MediaWiki? The version of CategoryTree you're using is 4 years old. Please upgrade.

Still, since you ask, the code you point to is called by the LanguageGetMagic hook. If you're really running MediaWiki 1.6, that explains the warning you're getting. Since that function doesn't use the value of $langCode, you can just change the function declaration to: function efCategoryTreeGetMagic( &$magicWords, $langCode = null ) {