public static function functionExists($function)
    {
        // eval() is a language construct
        if ($function == 'eval') {
            // does not check suhosin.executor.eval.whitelist (or blacklist)
            if (extension_loaded('suhosin')) {
                return @ini_get("suhosin.executor.disable_eval") != "1";
            }
            return true;
        }

        $exists = function_exists($function);

        if (extension_loaded('suhosin')) {
            $blacklist = @ini_get("suhosin.executor.func.blacklist");
            if (!empty($blacklist)) {
                $blacklistFunctions = array_map('strtolower', array_map('trim', explode(',', $blacklist)));
                return $exists && !in_array($function, $blacklistFunctions);
            }
        }

        return $exists;
    }