--TEST-- ReflectionParameter::getDefaultValue() should also work for parameters of internal functions. --FILE-- getMethod('setTime'); foreach ($method->getParameters() as $k => $parameter) { try { var_dump($parameter->getDefaultValue()); } catch (ReflectionException $exception) { echo $exception->getMessage() . "\n"; } } echo "----------\n"; $class = new ReflectionClass('DateTimeZone'); $method = $class->getMethod('listIdentifiers'); foreach ($method->getParameters() as $parameter) { try { var_dump($parameter->getDefaultValue()); } catch (ReflectionException $exception) { echo $exception->getMessage() . "\n"; } } ?> --EXPECT-- Internal error: Failed to retrieve the default value Internal error: Failed to retrieve the default value int(0) int(0) ---------- int(2047) NULL