--TEST-- ReflectionParameter::isDefaultValueConstant() should also work for parameters of internal functions --FILE-- getMethod('setTime'); foreach ($method->getParameters() as $parameter) { try { var_dump($parameter->isDefaultValueConstant()); } 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->isDefaultValueConstant()); } catch (ReflectionException $exception) { echo $exception->getMessage() . "\n"; } } ?> --EXPECT-- Internal error: Failed to retrieve the default value Internal error: Failed to retrieve the default value bool(false) bool(false) ---------- bool(true) bool(false)