private function loadExtTablesForExtension($extensionKey)
    {
        $extensionInfo = $GLOBALS['TYPO3_LOADED_EXT'][$extensionKey];
        // In general it is recommended to not rely on it to be globally defined in that
        // scope, but we can not prohibit this without breaking backwards compatibility
        global $T3_SERVICES, $T3_VAR, $TYPO3_CONF_VARS;
        global $TBE_MODULES, $TBE_MODULES_EXT, $TCA;
        global $PAGES_TYPES, $TBE_STYLES;
        global $_EXTKEY;
        // Load each ext_tables.php file of loaded extensions
        $_EXTKEY = $extensionKey;
        if (isset($extensionInfo['ext_tables.php']) && $extensionInfo['ext_tables.php']) {
            // $_EXTKEY and $_EXTCONF are available in ext_tables.php
            // and are explicitly set in cached file as well
            $_EXTCONF = $GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][$_EXTKEY];
            require $extensionInfo['ext_tables.php'];
        }
    }